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]

🦋 Changeset detected

Latest commit: 923daae

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	Major

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[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	97.47 KB (+0.39% 🔺)
packages/react/dist/browser.umd.js	97.71 KB (+0.21% 🔺)

[primer-integration]

👋 Hi from github/github! Your integration PR is ready: https://github.com/github/github/pull/342146