chore: Fixes embedded multiselect focus management

[pan-kot]

Description

The PR includes 2 fixes for embedded multiselect:

• Options are selectable with Space (same as for multiselect w/o filter);
• Focus highlight is removed when the list loses focus.

Screen.Recording.2024-10-18.at.10.06.10.mov

The change is needed for: #2739

How has this been tested?

• New unit tests

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

All modified and coverable lines are covered by tests ✅

Project coverage is 96.20%. Comparing base (7693793) to head (3970f85).
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2896      +/-   ##
==========================================
- Coverage   96.21%   96.20%   -0.01%     
==========================================
  Files         761      761              
  Lines       21490    21494       +4     
  Branches     7359     7353       -6     
==========================================
+ Hits        20676    20679       +3     
- Misses        761      807      +46     
+ Partials       53        8      -45     

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