install a whole bunch of gerrit plugins

i browsed again through the gerrit plugins hosted with gerrit itself; here's a list of what i think might make sense having. i suppose some might be actually already installed, but not being an admin i can't tell.

it would probably make sense to break out separate tasks after a quick triage.

user-visible features

codemirror-editor - built-in IDE, presumably better than the directly built-in change editing capabilities (unless that's actually already that plugin). Already installed

github - importing pull requests. certainly also requires integration of qt account with GH.

gitiles - instead of gitweb (on the gerrit server itself; unfortunately not applicable to code.qt.io). might be nicer/better integrated, but that needs exploration.

imagare - that's basically a built-in pastebin for images. it might make sense for teams who work on visual tooling.

image-diff - rich image diffs. predominantly for artwork creators, but might also help font rendering test cases or such.

its-jira - as a replacement for the gerrit bot, following up to QTQAINFRA-171. note that branch-related functionality may be still missing. Uses only Basic Authentication auth method, which is disabled in the Qt JIRA.

admin tools

messageoftheday (and possibly also motd) - post maintenance announcements directly on gerrit, as we can already do on jira.

plugin-manager

replication-status

rename-project (and possibly delete-project)

serviceuser - to easily create bot accounts without having to involve qt account.

singleusergroup - easier way to grant one-off permissions. otoh, it may
contribute to an utter mess if not used judiciously.

backends / enablers

avatars-external - to replace avatars-gravatar when qt account does own avatar management, which should be faster, more reliable, and more privacy-preserving than gravatar (note that qt account may pull from gravatar in turn).

batch - as a building block for a "more upstream-based" CI gating implementation. possibly in conjunction with the checks plugin (which is supposed to receive functionality related to gating).

hide-actions - to get rid of "rebase" and maybe others in a non-hacked way.

hooks - for a more direct (and thus reliable) integration with bots (that run directly on the gerrit server).