Time for new release: 5.2

[ZedThree]

The big coordinates refactor, #2873, is basically ready and is going to break most things (we have an automatic updater in boutdata to ease the transition!), and we've got a lot of fixes and some features in next since the last release, so it's time for a new one before we merge #2873 into next.

Are there any currently open PRs which people particularly want in 5.2? Or open issues which need fixing?