How can we release a major version based on v8?

[gfellerph]

Breaking changes with an Angular update prevent us from continuing to release v8. How can we release a new major version without touching main?

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1. Make sure the release/v9 branch does not get created on every push to the main branch (seems like a bug, because we have entries for every single v9.next version in the versions.json). This could be fixed already in advance, by checking if the second entry in the file has the same major version number or a next flag or something.
2. Make sure the release/v9 branch does not already exist or delete it.
3. !!! IMPORTANT !!! Release the v8, before you merge any breaking changes to it.
4. Create a release/v9 branch from the release/v8 branch.
5. Add breaking changes (namely the angular update to v19) to the release/v9 branch.
6. Follow the steps in the release.yaml workflow to release that branch manually.
7. If some of the steps in the release.yaml belong to the previous major version, do that on the release/v8 branch. If something belongs to the latest version, do it on the main branch (like updating the versions.json file, etc.).
8. Update the version numbers on the main branch to 10.x.x-next (not sure if this is necessary).