Migrate tools/toolsbeta grid to Debian Buster since Stretch is deprecated. This is mostly just adding Buster queues, but then Stretch queues need to go away.
[x] make sure exec grid works
[x] make sure webgen grid works -- mostly working, but double-check blocked by {T301117}
[x] make sure weblight grid works -- mostly working, but double-check blocked by {T301117}
[x] make sure jsub uses `stretch` as default release https://gerrit.wikimedia.org/r/plugins/gitiles/labs/toollabs/+/refs/heads/master/jobutils/bin/jsub#727
[x] make sure webservice uses `stretch` as default release https://gerrit.wikimedia.org/r/plugins/gitiles/operations/software/tools-webservice/+/refs/heads/master/scripts/webservice#239
[x] verify usrmerge stuff https://gerrit.wikimedia.org/r/c/operations/puppet/+/761684 (thanks @Majavah )
[x] make sure cron servers work in the new setup (specially with usrmerge stuff) [same as above]
About the migration itself, this will be handled by (@komla):
[] review migration instructions, make sure we document common pitfalls and errors.
[x] create migration timeline.
[] create migration communication plan.
[] make sure controls are in place so we have visibility about how the migration is proceeding (https://sge-status.toolforge.org/ and friends)
[] as an alternative to the stretch->buster migration, we would like to offer the alternative to migrate to k8s directly. Create wikitech docs for toolforge-jobs. See {T285944} and {T301665}
[] create plan for tools that don't migrate