…hProviders` to callback style interfaces (#48639)

walkProviderTree and processInjectorTypesWithProviders both perform some generic traversal logic of the import graph of an input NgModule or Standalone component. Currently, these functions pass around a `providersOut` array that is used to collect providers at each step of the traversal.

This PR converts those functions to accept visitor callbacks instead of the `providersOut` array. This is done to make the traversal logic of these functions reusable, while leaving it up to the visitor to determine the logic that fires for each visited node.

This refactor would allow us to reuse `walkProviderTree` for injector debugging APIs that could support some cool features in DevTools, like tracing the injector resolution path of an injected property on a component instance all the way up to the specific imported module/standalone component.

PR Close #48639

This commit introduces 3 new APIs.

getDependenciesFromInstantiation:
- Given an injector and a token that was instantiated by that injector, discover all of the things were injected in the instance of that token
- This API is meant to enable recursive inspection of dependencies. Dependencies returned by this API include which injector they were providedIn, which enables the continous use of getDependenciesFromInstantiation to determine the dependencies of dependencies

getInjectorProviders:
- Given an injector, discover all of the providers that were configured in that injector.
- This API returns information on the configured providers of an injector, including the import path that leads to the container that the provider originated from (NgModule or standalone directive). This enables fine grained inspection to determine where a specific provider comes from.

getInjectorParent:
- Given an injector, discover the parent of that injector.
- This function is meant to be used recursively to discover the entire resolution path from a starting injector to the NullInjector.

These APIs were designed to be used together. For example, getInjectorParent can be used to discover the structure of an injector hierarchy. Once that's done, getInjectorProviders can be used to determine the providers of each injector in that hierarchy.

Another example: getDependenciesFromInstantiation can be used to discover the dependencies of a specific injector constructed instance. From there, we can use getInjectorParent to discover the injector resolution path and map each dependency to a path from the starting injector to the injector that it was provided in.

PR Close #48639

…ng APIs (#48639)

    Creates unit tests for the following APIs

    - setInjectorProfiler
    - getInjectorProviders
    - getInjectorResolutionPath
    - getDependenciesFromInjectable

    Modifies existing tests in

    - packages/examples/core/di/ts/injector_spec.ts
    - packages/core/test/render3/jit/declare_injectable_spec.ts
    - packages/core/test/render3/jit/declare_factory_spec.ts

    because they setup framework injector context manually.

    Exports setInjectorProfilerContext in packages/core/src/core_private_export.ts in order for use
    in the the modified tests above.

PR Close #48639

…8639)

Currently, understanding dependency injection in Angular requires a lot of context and has been sited in our surveys as one of the largest points of confusion that our users have with the framework. This commit is the beginning of our approach to make debugging dependency injection in Angular easier.

This commit introduces injector profiler callbacks in parts of the framework to emit injector events. It also introduces a default handler for these events. This default handler parses the stream of events to construct some data structures that will support new injector debug APIs.

We have implemented a similar pattern in the past to minimize overhead. There is also the possiblity of making the internal `setInjectorProfiler` function a public debug API in the future, so that users can implement their own handlers to debug DI events. Lastly DI in Angular maps nicely to a stream of events.

For production applications there is no runtime overhead. For applications in dev mode there is some additional overhead from the default profiler handling injector events and holding debug data in memory.

For production applications, dead code elimination should strip all of the code used by this PR.

PR Close angular#48639

…hProviders` to callback style interfaces (angular#48639)

walkProviderTree and processInjectorTypesWithProviders both perform some generic traversal logic of the import graph of an input NgModule or Standalone component. Currently, these functions pass around a `providersOut` array that is used to collect providers at each step of the traversal.

This PR converts those functions to accept visitor callbacks instead of the `providersOut` array. This is done to make the traversal logic of these functions reusable, while leaving it up to the visitor to determine the logic that fires for each visited node.

This refactor would allow us to reuse `walkProviderTree` for injector debugging APIs that could support some cool features in DevTools, like tracing the injector resolution path of an injected property on a component instance all the way up to the specific imported module/standalone component.

PR Close angular#48639

This commit introduces 3 new APIs.

getDependenciesFromInstantiation:
- Given an injector and a token that was instantiated by that injector, discover all of the things were injected in the instance of that token
- This API is meant to enable recursive inspection of dependencies. Dependencies returned by this API include which injector they were providedIn, which enables the continous use of getDependenciesFromInstantiation to determine the dependencies of dependencies

getInjectorProviders:
- Given an injector, discover all of the providers that were configured in that injector.
- This API returns information on the configured providers of an injector, including the import path that leads to the container that the provider originated from (NgModule or standalone directive). This enables fine grained inspection to determine where a specific provider comes from.

getInjectorParent:
- Given an injector, discover the parent of that injector.
- This function is meant to be used recursively to discover the entire resolution path from a starting injector to the NullInjector.

These APIs were designed to be used together. For example, getInjectorParent can be used to discover the structure of an injector hierarchy. Once that's done, getInjectorProviders can be used to determine the providers of each injector in that hierarchy.

Another example: getDependenciesFromInstantiation can be used to discover the dependencies of a specific injector constructed instance. From there, we can use getInjectorParent to discover the injector resolution path and map each dependency to a path from the starting injector to the injector that it was provided in.

PR Close angular#48639

…ng APIs (angular#48639)

    Creates unit tests for the following APIs

    - setInjectorProfiler
    - getInjectorProviders
    - getInjectorResolutionPath
    - getDependenciesFromInjectable

    Modifies existing tests in

    - packages/examples/core/di/ts/injector_spec.ts
    - packages/core/test/render3/jit/declare_injectable_spec.ts
    - packages/core/test/render3/jit/declare_factory_spec.ts

    because they setup framework injector context manually.

    Exports setInjectorProfilerContext in packages/core/src/core_private_export.ts in order for use
    in the the modified tests above.

PR Close angular#48639