fix(forms): Allow canceled async validators to emit.

[JeanMeche]

With this change, If an async validator that should have emitted was cancelled by a non-emitting validator, the status change will be reported on the AbstractControl.events observable.

This issue can happen when a FormControl is added to a FormGroup and a FormGroupDirective/FormControlDirective trigger a non-emitting validation (which cancels the initial validator execution).

Note: The behavior remains the same of the existing statusChanges observable as the change was too breaking to land in G3.

fixes: #41519

[crisbeto]

TGP for future reference.

[dylhunn]

Matthieu and i spent some time yesterday looking at the failures, and they mostly originate with various teams using setTimeout trick to poll the status changes. We reached out to some of them to see if we can get them fixed, but if not, we will ship this enabled only for the new unified control state change API.

[dylhunn]

Talking to a possible owner of a failing test in g3, in order to get some help fixing the test.

[JeanMeche]

Since this change is a bit too breaking to land in G3, I'm looking at a solution that will only work with the new events observable.

[dylhunn]

caretaker: this has a clean TGP (https://test.corp.google.com/OCL:630752820:BASE:630752881:1714884722829:6f76c7bc)

[atscott]

This PR was merged into the repository by commit 53b0d6a.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}