Test suite does not compare any h.bgc streams #357

#323 pointed out that mom6.h.bgc.native was ignored in baseline comparisons, and only mom6.h.bgc.z was tested. A bug in config_archive.xml combines with #356 to result in mom6.h.bgc.z being omitted in testing as well. A fix (that will compare a single block of mom6.h.bgc.z given #356) is

     <!-- match filenames of the form
-         h.bgc.*[._optional instance number].nc -->
-    <hist_file_extension>h\.bgc\..*(\._\d+)?\.nc$</hist_file_extension>
+         h.bgc.*[._optional instance number].nc[.optional tile number] -->
+    <hist_file_extension>h\.bgc\..*(\._\d+)?\.nc(\.\d*)?(\.gz)?$</hist_file_extension>

I'm going to add this fix to #355 -- it's not strictly related to the MARBL diagnostics for CMIP, but is necessary for getting at least some test coverage so it seems fitting.