backport: Add 9.4 branch

[elastic-vault-github-plugin-prod]

Merge as soon as 9.4 branch was created. Auto-merge is not yet supported, see Mergifyio/mergify#2821

[mergify]

This pull request does not have a backport label. Could you fix it @elastic-vault-github-plugin-prod[bot]? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b add-backport-next-9.5.0 upstream/add-backport-next-9.5.0
git merge upstream/main
git push upstream add-backport-next-9.5.0