feat: Add public design tokens to slider

[amanabiy]

Description

This PR makes the following design tokens public to resolve customer feature request for themeable Slider component:

Tested by running in the pipeline

Related links, issue #: AWSUI-61611

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 97.14%. Comparing base (69239f6) to head (61d13f4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4178   +/-   ##
=======================================
  Coverage   97.14%   97.14%           
=======================================
  Files         873      873           
  Lines       25653    25653           
  Branches     9284     9284           
=======================================
  Hits        24921    24921           
  Misses        685      685           
  Partials       47       47           

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[gethinwebster]

I think there's not really a need to add this page - let's skip it unless you have a strong reason to keep it, to keep our pages dir from growing too large

[amanabiy]

I see. It was helpful for me to do the tests and share how it works. I removed it.

[gethinwebster]

I think it would probably make more sense to have the new Range tokens reference the Handle tokens rather than redefining the same values

[amanabiy]

Makes sense, changed it to reference the handle tokens.