feat: Use a centralized announcer to make aria-live announcements

[avinashbot]

Description

Introduces the live region component internally! See the internal docs for motivation and improvements, but the big improvements are the lack of double-text when LiveRegion is used, grouped and debounced updates across multiple local live regions, including custom components in the future.

See: tXwQOO7xEK8T

How has this been tested?

Unit tests and integration tests - most existing tests pass, but some failing ones have been updated to handle the lack of a local live region.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

Attention: Patch coverage is 93.80531% with 7 lines in your changes missing coverage. Please review.

Project coverage is 96.19%. Comparing base (7693793) to head (264abac).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
src/internal/components/live-region/controller.ts	88.37%	5 Missing ⚠️
src/button/internal.tsx	75.00%	1 Missing ⚠️
src/internal/components/live-region/internal.tsx	97.36%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2128      +/-   ##
==========================================
- Coverage   96.21%   96.19%   -0.03%     
==========================================
  Files         761      764       +3     
  Lines       21490    21552      +62     
  Branches     7359     6973     -386     
==========================================
+ Hits        20676    20731      +55     
- Misses        761      813      +52     
+ Partials       53        8      -45     

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