Bug 1897403 - Handle wpt test id as a URL when computing group name, r=Sasha

wpt test ids are URLs, and can have query components. This means that
using `os.path.dirname` isn't a correct way to extract different parts
of the URL

In particular a test id like `/foo/bar/baz?foobar=sp/am` can lead to an
invalid group name like `foo/bar/baz?foobar=sp`, which breaks the
invariant that we can turn the group name into a filesystem path that
may contain a __dir__.ini file with metadata for that group.

The fix here is to correctly treat the test id as a URL using the same
logic as in wptrunner.

Differential Revision: https://phabricator.services.mozilla.com/D210783

testing/mozbase/moztest/moztest/resolve.py

@@ -8,6 +8,7 @@ import pickle
 import sys
 from abc import ABCMeta, abstractmethod
 from collections import defaultdict
+from urllib.parse import urlsplit
 
 import mozpack.path as mozpath
 import six
@@ -853,10 +854,9 @@ class TestResolver(MozbuildObject):
         if test["name"].startswith("/_mozilla/webgpu"):
             depth = 9001
 
-        group = os.path.dirname(test["name"])
-        while group.count("/") > depth:
-            group = os.path.dirname(group)
-        return group
+        # We have a leading / so the first component is always ""
+        components = depth + 1
+        return "/".join(urlsplit(test["name"]).path.split("/")[:-1][:components])
 
     def add_wpt_manifest_data(self):
         """Adds manifest data for web-platform-tests into the list of available tests.