Indexer: Add metaTags and make autodocs inherit them

[shilman]

Telescopes off #25328

What I did

In the current code, the Autodocs index entry inherits all the tags from the "primary" (first) story on the page it is being generated from. This results in the following weird behavior.

Suppose I have a component Foo with three stories, A, B, and C. The component's meta adds the autodocs tag, meaning that the sidebar shows "Foo > Autodocs, A, B, C". A has the tags ['a']. Then I filter the sidebar to remove everything with the tag 'a'. The story A disappears as expected, but the autodocs also disappears because it inherits all of A's tags!

This change means that the Autodocs entry only inherit's the CSF meta tags. So if the meta has tags ['m'] and I exclude 'm', it will remove Autodocs and A, B, C because the stories also inherit meta's tags. If I exclude 'a', it will only exclude A (and any other entries tagged with 'a')

NOTE: this PR doesn't fix the behavior for attached MDX pages, which currently don't inherit any tags. So that is a known corner case bug.

NOTE: this extends the Indexer API. I think this is OK because: (1) the API is still experimental, and (2) we already include metaId in the API, so this is consistent with that.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

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core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

[tmeasday]

Tests are great!

Maybe you should also add some test of what the behaviour is when you browse directly to a hidden story.