next month we need to be ready for ESR91.

steps to do this:
https://moz-releng-docs.readthedocs.io/en/latest/procedures/release-duty/desktop/esr-to-esr-updates.html

prior art: bug 1644817

potentially need to support fixes like:
https://bugzilla.mozilla.org/show_bug.cgi?id=1647347
https://bugzilla.mozilla.org/show_bug.cgi?id=1649383
https://bugzilla.mozilla.org/show_bug.cgi?id=1637549

there might be other things like shipit, fenix, android-components, devedition, webrender/fission, or other things.

Note to self: to check how mergeduty scripts are being impacted by this?
Note to self 2: should we document this in moz-releng-docs.readthedocs.io/ as we go on so that next time this is slightly better?

302 to comment 2

There's a couple of patches flying around that Julien put up, assigning this to him to avoid stepping toes.

mozilla-version needed an update in both shipit (to be able to schedule releases) and treescript (for the release-to-esr migration)

Another tweak: removed the firefox-esr78-localtest rule in balrog from the esr-localtest-next channel (restricting it to esr-localtest instead of esr-localtest*), to let update-verify-next jobs pass. And same for cdntest.