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

[kruskall]

extend the check to all remaining repositories

[github-actions]

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[bmorelli25]

This is incredible

[bmorelli25]

@elastic/docs-build-guild any reservations or thoughts before I merge this? This PR adds on to #3066.

This PR enables all documentation repositories (except Kibana) to exist the documentation build early if there are no doc-related changes. This will save time and money. For all enabled repos, we fetch the latest changes from the target branch of the pull request and check for changes in specified files and directories with git diff.