ci: Fix non-freedreno performance jobs running during Marge merges.

ci: Fix non-freedreno performance jobs running during Marge merges.

I mistakenly applied .gl-rules to the non-freedreno perf jobs, which
caused them to be incorrectly run pre-merge when core GL files changed.
Pull the freedreno core GL performance job rules out, explain a bit more
what is going on, and use it from iris and virgl performance testing.

This also drops running freedreno performance when core vulkan files
change -- freedreno perf testing doesn't have any turnip usage, nor does
it watch for turnip file changes.

Acked-by: Michel Dänzer <mdaenzer@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17386>