chore: Use CSS-native :focus-visible to track visible focus state (batch 3)

[avinashbot]

Description

Reducing the potential blast radius of a visual change that affects tons of components. I'll be removing the internal JS-based focus-visible solution in individual batches. This one contains all the weird interesting changes I've had to make, but it's the last one before I remove useFocusVisible() from the components package entirely.

See #3585 for the big original PR.

Related links, issue #, if available: AWSUI-60845

How has this been tested?

Tested the whole big PR in my dev pipeline, and the individual changes just manually.

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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.59%. Comparing base (c606ac5) to head (bf57dd9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3607   +/-   ##
=======================================
  Coverage   96.59%   96.59%           
=======================================
  Files         807      807           
  Lines       23582    23582           
  Branches     8261     8271   +10     
=======================================
  Hits        22780    22780           
+ Misses        795      748   -47     
- Partials        7       54   +47     

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