Merge all group tests

These tests are basically stateless and don't require any test setup.
Avoid having to spin up Gerrit servers in 8 separate VMs and
concatenate all the test methods together.

This change simply moves method bodies, with minor method reordering;
cleanup changes to methods are left to a followup, to make them
easier to review.

Change-Id: Ifc620f7051c661a5c51a6b86810d92f0c46de1b2