This commit refactors the way we store validators in AbstractControl-based classes:
in addition to the combined validators function that we have, we also store the original list of validators.
This is needed to have an ability to clean them up later at destroy time (currently it's problematic since
they are combined in a single function).
The change preserves backwards compatibility by making sure public APIs stay the same.
The only public API update is the change to the `AbstractControl` class constructor to extend the set
of possible types that it can accept and process (which should not be breaking).
PR Close#37881
Moves the public api .d.ts files from tools/public_api_guard to
goldens/public-api.
Additionally, provides a README in the goldens directory and a script
assist in testing the current state of the repo against the goldens as
well as a command for accepting all changes to the goldens in a single
command.
PR Close#35768
Andrew Kushnir
Joey Perrott