…46646)

Due to the restrictions of circular dependency checking, we need a separate
internal interface for a renderer. We cannot use `Renderer2` as a type
internally as even importing it as a type incurs a dependency on its
implementation, which creates a major potential for circular dependencies.

Previously this role was served by the `Renderer3` type. As we prepare to
remove the `Renderer3` abstraction (the idea of using `document` as a
differently-shaped renderer), this commit renames `ProceduralRenderer3` to
the more generic term `Renderer`.

`RendererFactory3` is also renamed to the more generic `RendererFactory` for
consistency.

PR Close #46646

This commit migrates any remaining Angular tests which are using some form
of Renderer3 interfaces. Instead, they're switched to Renderer2.

PR Close #46646

Previously, when instantiating a component, Angular would look in the DI
hierarchy for `RendererFactory2`. Any DI tree which rolls up through an
application injector (that is, one created with `BrowserModule`) should be
able to provide this interface. If not found, Angular would switch to the
experimental `Renderer3` mechanism. This switch was designed this way,
because it allowed for the creation of experimental applications where
`RendererFactory2` was not included in the bundle at all.

In this commit, instead of automatically falling back on `Renderer3`-style
rendering, an error is raised instead if `RendererFactory2` is missing from
the DI hierarchy.

PR Close #46646

This commit removes the `Renderer3` experiment which attempted to use the
real DOM API as Angular's renderer. As shown in the diff, having this
experiment around added real code complexity to Angular that could not be
removed by an optimizer.

Since we no longer feel this experiment is worth continuing, we're removing
the `Renderer3` concept and all supporting code.

PR Close #46646

This commit removes the experimental `renderComponent` operation, which
implemented an alternative, lighter-weight bootstrapping option. This
experiment is being discontinued as the path towards it being a supported
production API was not clear. In particular, it lacked a clear roadmap for
supporting Angular's change detection, particularly when consuming existing
components.

PR Close #46646