MR approval check for noise changes

This series creates a new procedure for validating/approving noise changes in merge requests.

A special CI job is added that runs only on merge requests that update the test git ref, indicating that a noise has been changed. The MR will show present a report of the changed noises, and will block on MR approval. Once approval has been given, the review:check_approval job can be re-run, which should now pass, allowing the MR to proceed.

If the noises change but the reference has not been updated, then the CI pipeline will fail as usual.

See the updates to CONTRIBUTING for more details.

gwinc/test/__main__.py

@@ -14,7 +14,7 @@ from collections.abc import Mapping
 from PyPDF2 import PdfFileReader, PdfFileWriter
 
 from .. import IFOS, load_budget
-from ..io import load_hdf5, save_hdf5
+from ..io import load_hdf5
 
 try:
     import inspiral_range