misc: Add weekly tests to Github workflows

This introduces the very-long tests from our weekly tests to be
able to run within GitHub.

Change-Id: I5f5b4c521b47272cb27640c572a869c26c04b95a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/71401
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>