feat(docs): autogenerate API documentation

[aramissennyeydd]

Hey, I just made a Pull Request!

Addresses #26894.

This uses https://github.com/PaloAltoNetworks/docusaurus-openapi-docs to render our existing specs. The goal here is to make the OpenAPI spec the source of truth for docs + API definition. I moved the existing catalog docs into the spec and saw really nice results in the autogenerated markdown.

TODO:

• Figure out a better balance of stored in git vs generated.

✔️ Checklist

• A changeset describing the change and affected packages. (more info)
• Added or updated documentation
• Tests for new functionality and regression tests for bug fixes
• Screenshots attached (for UI changes)
• All your commits have a Signed-off-by line in the message. (more info)

[backstage-goalie]

Missing Changesets

The following package(s) are changed by this PR but do not have a changeset:

• @backstage/plugin-catalog-backend

See CONTRIBUTING.md for more information about how to add changesets.

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
@backstage/plugin-catalog-backend	plugins/catalog-backend	none	v1.28.1-next.0

[backstage-goalie]

Thanks for the contribution!
All commits need to be DCO signed before they are reviewed. Please refer to the the DCO section in CONTRIBUTING.md or the DCO status for more info.

[awanlin]

This looks like a great addition to the docs @aramissennyeydd, thanks for taking this on!

Looks good over all, curious about two things:

1. Whats the impact on build time?
2. Do we need to manage the new sidebars manually?