Prepare 12.7.1 release

Release issue: gitlab-org/release/tasks#1179 (closed)

Summary

This MR prepares 12-7-stable for 12.7.1.

Automated cherry-picking

Merge requests labeled ~"Pick into 12.7" should be automatically picked into this MR using the following ChatOps command:

# In Slack
/chatops run release merge 12.7.1