This adds a new morph template for modifying a task's env and the corresponding glue
to specify it from |mach try fuzzy|. It can be used like:
./mach try fuzzy --env FOO=1 --env BAR=baz
This will simply set those environment variables in *all* tasks. We could add the
ability to only specify it for a subset of tasks in the future, but that seems like
a hard problem that probably isn't worth it.
MozReview-Commit-ID: C4sokv886PU
--HG--
extra : rebase_source : 64c9105848e6becd33fae63aeabc3423cfda3bdf