now that we have all tasks with a variant (i.e. fission, no-fission, 1proc, etc.) we can remove fission and make it default. Likewise for all combined variants (socketprocess-fission) should will have the fission tag removed.

work will primarily be done within the taskcluster/ folder. Some transforms will need adjustment, and cleaning up the treeherder group symbols. While adjusting this, we should remove the e10s part of the label as that is not needed anymore.

We need to be aware of:

• perf jobs have all the right tags (retain metadata about e10s and fission)
• android jobs run as expected with the same labels (or make sure they still run)
• any tools that might depend on the name (i.e. backfill, ./mach ..., sql queries) - specifically ensure that if we remove -fis and -e10s from the task label that we don't have tools expecting it (query searchfox should be adequate enough)

There should be no work needed in mozharness or actual test harnesses, all of the harnesses have --disable-fission where it is needed and assume fission by default.

When this bug is resolved, the work of fission-by-default for desktop will be completed.

https://hg.mozilla.org/mozilla-central/rev/f0682128deb8