PageHeader data-component major changes

[llastflowers]

Relates to https://github.com/github/primer/issues/6501

Changelog

New

Update instances of data-component names that use PH_ to PageHeader., and also update data-component="TitleArea" to data-component="PageHeader.TitleArea" per ADR-023.

Rollout strategy

• Patch release
• Minor release
• Major release; if selected, include a written rollout or migration plan
• None; if selected, include a brief description as to why

Files to update in dotcom (as of opening this PR):

• packages/commits/components/Commit/header/CommitHeader.module.css
• packages/pull-requests/components/tests/PullRequestHeader.browser.test.tsx
• packages/pull-requests/components/PullRequestHeader.module.css

Search to confirm: https://github.com/search?q=repo%3Agithub%2Fgithub-ui+PH_&type=code&p=2 & https://github.com/search?q=repo%3Agithub%2Fgithub-ui+data-component%3D%27TitleArea%27&type=code

Testing & Reviewing

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-ui (Learn more about how to run integration tests)

[changeset-bot]

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Latest commit: 0058268

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[github-actions]

⚠️ Action required

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. Check the integration testing docs for step-by-step instructions. Or, apply the integration-tests: skipped manually label to skip these checks.

To publish a canary release for integration testing, apply the Canary Release label to this PR.