Upgrade shiki to v0.14.1

[bluwy]

Changes

Fixes #6899

• Upgrade shiki
• Add compat code to handle shiki breaking changes
  • AFAICT the only breaking change is the theme name change, so I added compat to remap the old theme name to the newer one.
• Clean up shiki theme and language codegen
• Add theme name to pre tag class, e.g. <pre class="astro-code github-dark"> (feature by shiki itself)

NOTE: while this could break theme types in shikiConfig, they will still work in runtime so I don't think this is a breaking change.

Testing

Existing tests should pass. I also tested the <Code component locally so it still works, including the compat stuff.

Docs

The only new thing to document is probably the theme name in the pre tag, but I'm not sure if it needs to be documented specifically.

[changeset-bot]

🦋 Changeset detected

Latest commit: 4e3a99f

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

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[github-actions]

This PR is blocked because it contains a minor changeset. A reviewer will merge this at the next release if approved.

[bluwy]

This is ready for review now. I added additional comments on some changes above that are minimized to keep this page clean.