Move fake gerrit and pagure into dedicated files

This change is merely a reorganization to move the fake gerrit and
gitlab classes into their own files to match github and gitlab.

The Fake*Connection classes for all 4 drivers are also moved into
their respective files.  This is accomplished by moving some symbols
from base.py into a new tests/util.py to resolve the import cycle
(which is likely why they were not there in the first place).

Change-Id: I274b9e5abf6086656f8ceb5a16dab2f8393deead

tests/util.py

@@ -0,0 +1,25 @@
+# Copyright 2012 Hewlett-Packard Development Company, L.P.
+# Copyright 2016 Red Hat, Inc.
+# Copyright 2021-2024 Acme Gating, LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import os
+import random
+import hashlib
+
+FIXTURE_DIR = os.path.join(os.path.dirname(__file__), 'fixtures')
+
+
+def random_sha1():
+    return hashlib.sha1(str(random.random()).encode('ascii')).hexdigest()