refactor(ButtonBase): To use CSS modules behind the feature flag

[langermank]

Part of https://github.com/github/primer/issues/3815

Changelog

Changed

• The ButtonBase component uses CSS modules behind the flag

Rollout strategy

• Minor release

Testing & Reviewing

Snapshots should match with flag on/off

Merge checklist

• [ ] Added/updated tests
• [ ] Added/updated documentation
• [ ] Added/updated previews (Storybook)
• [ ] Changes are SSR compatible
• [ ] Tested in Chrome
• [ ] Tested in Firefox
• [ ] Tested in Safari
• [ ] Tested in Edge
• [ ] (GitHub staff only) Integration tests pass at github/github (Learn more about how to run integration tests)

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: b0bd7ad1d66a6f2aed836a3ca54d752e714455cf

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Minor

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[github-actions[bot]]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	96.85 KB (+0.23% 🔺)
packages/react/dist/browser.umd.js	97.28 KB (+0.4% 🔺)

[primer-integration[bot]]

:wave: Hi from github/github! Your integration PR is ready: https://github.com/github/github/pull/339048