Rename the mobile_static profile to aot_only

Rename the mobile_static profile to aot_only

We decided it's a better name since we're using the profile to
test FullAOT scenarios on desktop (as opposed to the mobile profiles).

While doing the rename I saw that a lot of the #ifdefs were using
MOBILE_STATIC even though the code should actually be included/excluded
in all FullAOT scenarios, e.g. System.Reflection.Emit. I replaced those
cases with FULL_AOT_RUNTIME instead.

For cases where code is specific to this profile, I added a new
AOT_ONLY_DESKTOP define.