Bug 1643689 - [taskgraph] enable manifest-scheduling on autoland, r=marco

Sets autoland to use the 'bugbug' test manifest loader. This is being enabled
as part of a temporary trial to see the impact it has on sheriffing.

Depends on D90159

Differential Revision: https://phabricator.services.mozilla.com/D90160

taskcluster/taskgraph/decision.py

@@ -76,6 +76,7 @@ PER_PROJECT_PARAMETERS = {
     'autoland': {
         'optimize_strategies': 'taskgraph.optimize:project.autoland',
         'target_tasks_method': 'autoland_tasks',
+        'test_manifest_loader': 'bugbug',  # Remove this line to disable "manifest scheduling".
     },
 
     'mozilla-central': {

taskcluster/taskgraph/optimize/__init__.py

@@ -564,7 +564,9 @@ class project(object):
                 # The actual test strategy applied to regular pushes.
                 Any(
                     'skip-unless-schedules',
-                    'bugbug-reduced-fallback',
+                    'bugbug-reduced-manifests-fallback',
+                    'platform-disperse',
+                    split_args=split_bugbug_arg,
                 ),
             ),
         ),