Use Celery instead of RQ.

Celery provides a more robust set of queueing options for both tasks and
worker processes. Updates include:
- infrastructure necessary to run Celery, including celery entrypoint
- backgrounded functions are now imported directly from atst.jobs
- update tests as-needed
- update kubernetes worker pod command

tests/conftest.py

@@ -9,7 +9,6 @@ from collections import OrderedDict
 
 from atst.app import make_app, make_config
 from atst.database import db as _db
-from atst.queue import queue as atst_queue
 import tests.factories as factories
 from tests.mocks import PDF_FILENAME, PDF_FILENAME2
 from tests.utils import FakeLogger, FakeNotificationSender
@@ -158,12 +157,6 @@ def extended_financial_verification_data(pdf_upload):
     }
 
 
-@pytest.fixture(scope="function", autouse=True)
-def queue():
-    yield atst_queue
-    atst_queue.get_queue().empty()
-
-
 @pytest.fixture
 def crl_failover_open_app(app):
     app.config.update({"CRL_FAIL_OPEN": True})