chore: Move shared table-role and async-store primitives from components

[gethinwebster]

Description

Moves table-role (grid navigation + ARIA role helpers) and async-store out of @cloudscape-design/components into component-toolkit so the existing Table and the upcoming BasicTable/VirtualTable can share them.

Byte-identical move (no behaviour change); adds two entrypoints: ./internal/table-role and ./internal/async-store.
Related links, issue #, if available: n/a

How has this been tested?

• New/moved unit tests for table-role (grid-navigation, grid-navigation-processor, table-role-helper, utils) and async-store pass in the toolkit build.
• Verified downstream: @cloudscape-design/components was repointed locally to consume these via the new entrypoints; Table suites pass against the shared modules.

(Code will be removed from components repo once this package is merged & published, WIP: https://github.com/cloudscape-design/components/pull/4846/changes)

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

❌ Patch coverage is 98.98734% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.07%. Comparing base (a7d0d07) to head (1bef45e).

Files with missing lines	Patch %	Lines
src/internal/table-role/grid-navigation.tsx	98.31%	3 Missing ⚠️
src/internal/table-role/utils.ts	99.01%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #242      +/-   ##
==========================================
- Coverage   99.01%   98.07%   -0.94%     
==========================================
  Files          44       52       +8     
  Lines        1314     1764     +450     
  Branches      341      492     +151     
==========================================
+ Hits         1301     1730     +429     
- Misses         13       34      +21     

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