feat: Makes file token group public

[katiegeorge]

Description

This pulls file token group out of internal and into the public folder.

This PR is part one of multiple for file upload decomposition, to make the pull requests easier to review.

Full plan:

• File dropzone (internal)
• File input (internal)
• File token group (internal)
• File dropzone (external)
• File input (external)
• File token group (external) - this PR
• Adding file-upload variant to button group

Related links, issue #, if available: n/a

How has this been tested?

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 96.30%. Comparing base (6539f15) to head (dcabba7).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #3000    +/-   ##
========================================
  Coverage   96.30%   96.30%            
========================================
  Files         771      772     +1     
  Lines       21820    21825     +5     
  Branches     7450     7051   -399     
========================================
+ Hits        21013    21018     +5     
  Misses        799      799            
  Partials        8        8            

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[katiegeorge]

Closed in favor of combined PR: #3001