…nd visibility (#54981)

This commit changes the TypeScript reflection host to:

* inspect / process ES private fields. e.g. `#someField` — those are
  ignored right now and we would want to check them to issue
  diagnostics.

* determine an access level of a class member. E.g. a member may be
  public, may be private, may be ES private, or public readonly. This
  can then be used in various checks later.

PR Close #54981

…r APIs (#54981)

An initializer API like `input`, `output`, or signal queries may not be
compatible with certain access levels. E.g. queries cannot work with ES
private class fields.

This commit introduces a check for access levels into the initializer
API recognition— enforcing that every initializer API *clearly*
specifies what type of access is allowed.

PR Close #54981

…ivate fields (#54981)

This commit ensures that the new APIs like `input`, `model`, `output`,
or signal-based queries are not accidentally used on fields that have a
problematic visibility/access level that won't work.

For example, queries defined using a private identifier (e.g. `#bla`)
will not be accessible by the Angular runtime and therefore _dont_ work.

This commit ensures:

- `input` is only declared via public and protected fields.
- `output` is only declared via public and protected fields.
- `model` is only declared via public and protected fields.
- signal queries are only declared via public, protected and TS private
  fields (`private` works, while `#bla` does not).

Fixes #54863.

PR Close #54981

…nosticError` (#54981)

For `FatalDiagnosticError` we are currently hiding the `message` string
field in favor of the actual TS `diagnosticMessage`.

This works as expected, but makes these errors hard to debug in certain
environments (e.g. Jasmine). That is because `null` is the value of
`message` at runtime. We fix this by just overriding the type, like we
originally intended to do.

In addition, we properly render message chains in the `Error#message`
field— so that these errors, when uncaught, are somewhat reasonable and
can be useful.

PR Close #54981