upgrade to partitions without a costly bulk data migration

keep pre-upgrade events in an old table (instead of a partition)

- instead of creating a default partition, keep all events in special
"unpartitioned" tables
- track these tables via distinct proxy=true models
- when generating the queryset for a UnifiedJob's events, look at the
  creation date of the job; if it's before the date of the migration,
  query on the old unpartitioned table, otherwise use the more modern table
  that provides auto-partitioning

awx/main/access.py

@@ -45,6 +45,7 @@ from awx.main.models import (
     InventoryUpdateEvent,
     Job,
     JobEvent,
+    UnpartitionedJobEvent,
     JobHostSummary,
     JobLaunchConfig,
     JobTemplate,
@@ -2352,6 +2353,11 @@ class JobEventAccess(BaseAccess):
         return False
 
 
+class UnpartitionedJobEventAccess(JobEventAccess):
+
+    model = UnpartitionedJobEvent
+
+
 class ProjectUpdateEventAccess(BaseAccess):
     """
     I can see project update event records whenever I can access the project update
@@ -2895,3 +2901,4 @@ class WorkflowApprovalTemplateAccess(BaseAccess):
 
 for cls in BaseAccess.__subclasses__():
     access_registry[cls.model] = cls
+access_registry[UnpartitionedJobEvent] = UnpartitionedJobEventAccess