feat(material/chips): add unit tests for custom aria-describedby

[RobertAKARobin]

Continuation of #24292

See also #24644 for MatSelect

[andrewseguin]

This component will soon be deprecated in favor of the MDC one. Can you add this test there as well?

[RobertAKARobin]

@andrewseguin Unfortunately it seems I can't run the tests due to using a newer Macbook. I followed the steps here #23983 (comment) but no dice.

[devversion]

@RobertAKARobin M1 should work to my knowledge. We should close the issue, unless you have more details.

[RobertAKARobin]

@devversion I'll follow up in that other issue. Once I've got yarn test mdc-chips working I'd be happy to update this.

[RobertAKARobin]

@devversion Updated! The mat-chips specs test its usage in mat-form-field, but there aren't any existing FormField specs for mdc-chips. Adding all that felt like it was outside the scope of this PR.

[devversion]

Is the getter/setter needed here? Also I lack a little on context for this change I feel like. I thought we only needed the custom input when a component was a FormFieldControl where we also added additional described by ids automatically, using .setDescribedByIds

[RobertAKARobin]

@andrewseguin Can you explain a bit more about what changes you were looking for?

@devversion Yes, the getters/setters seem unnecessary. I was copying from the mat-chips code (which in turn was copied from mat-select, IIRC). Will wait to see what Andrew says though.