Move system install tests into normal CI (#2312)
Giving this a try... just making all of these a normal part of CI.
This is probably slightly slower than our normal CI, but not by much (it
depends how bad of a roll we get on the Windows network performance).
Includes #2309 to reduce the overhead of adding more platforms.
Alternatively, we could gate these with a label and just run on main by
default (i.e. #2308)
