feat(all): only build docs if there's a doc change

[kruskall]

extend the check to all remaining repositories

[github-actions[bot]]

A documentation preview will be available soon.

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* Rebuild this PR: `run docs-build` * Rebuild this PR and all Elastic docs: `run docs-build rebuild` _{`run docs-build` is much faster than `run docs-build rebuild`. A `rebuild` should only be needed in rare situations. If your PR continues to fail for an unknown reason, the doc build pipeline may be broken. Elastic employees can check the pipeline status [here](https://buildkite.com/elastic/docs-build).}

[bmorelli25]

This is incredible