WIP: Prepare 12.10.4-ee release

Release issue: gitlab-org/release/tasks#1321 (closed)

Summary

This MR prepares 12-10-stable-ee for 12.10.4-ee.

Automated cherry-picking

Merge requests labeled ~"Pick into 12.10" should be automatically picked into this MR using the following ChatOps command:

# In Slack
/chatops run release merge 12.10.4