manifest: Make include groups propagate to extend-project elements

Any groups specified to an include element should propagate to any
extend-project elements and then on to the projects.

Change-Id: I62b95689cc13660858564ae569cbfd095961ecc7
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/525321
Tested-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Commit-Queue: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

manifest_xml.py

@@ -1335,7 +1335,10 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                         f"failed parsing included manifest {name}: {e}"
                     )
             else:
-                if parent_groups and node.nodeName == "project":
+                if parent_groups and node.nodeName in (
+                    "project",
+                    "extend-project",
+                ):
                     nodeGroups = parent_groups
                     if node.hasAttribute("groups"):
                         nodeGroups = (