Prepare 10.5 RC4 release

Main release issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/42764

Summary

This MR prepares 10-5-stable for %10.5 (RC4) by merging 10-5-stable-prepare-rc4 into 10-5-stable.

MR Filter for ~"Pick into 10.5" MRs

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests?label_name%5B%5D=Pick+into+10.5&scope=all&state=merged

Note to leave in MRs

Picked into https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/17055, will merge into `10-5-stable` ready for `10.5 RC4`

/unlabel ~"Pick into 10.5"

Steps

1. Cherry-pick commits into this MR using the link for ~"Pick into 10.5" above.

• This can be done by checking out 10-5-stable-prepare-rc4 locally and using git cherry-pick -m1 MERGE_COMMIT_SHA

1. Push changes every so often and verify that the MR has been included
2. Leave a note in the MR so others can easily see that it is on track to be included in a release.

• Remove the ~"Pick into 10.5" label.

1. If there are any conflicts while picking MRs then attempt to resolve them; otherwise, create a new MR against the 10-5-stable-prepare-rc4 branch and assign it to the author of the conflicting files.
2. Merge CE-to-EE using one of the workflows described in the Merge CE stable changes to EE docs
3. Once this MR is green merge it to stable, preferably with a manual fast-forward merge to minimize waiting time, as described in Merging preparation MRs into stable

Checklist

• Changes marked ~"Pick into 10.5" have been picked

• Conflicts resolved

• No new commits have introduced directly to the stable branch while this MR was in progress. If there are, ensure these are merged into EE and check for a green pipeline after merging this MR.