django_api: Rename 'send_event' to 'send_event_rollback_unsafe'.

This commit renames the 'send_event' function to
'send_event_rollback_unsafe' to reflect the fact that it doesn't
wait for the db transaction (within which it gets called, if any)
to commit and sends event irrespective of commit or rollback.

In most of the cases we don't want to send event in the case of
rollbacks, so the caller should be aware that calling the function
directly is rollback unsafe.

zerver/lib/test_classes.py

@@ -2052,11 +2052,11 @@ class ZulipTestCase(ZulipTestCaseMixin, TestCase):
         # So explicitly change parameter name to 'notice' to work around this problem
         with (
             mock.patch("zerver.tornado.event_queue.process_notification", lst.append),
-            # Some `send_event` calls need to be executed only after the current transaction
-            # commits (using `on_commit` hooks). Because the transaction in Django tests never
-            # commits (rather, gets rolled back after the test completes), such events would
-            # never be sent in tests, and we would be unable to verify them. Hence, we use
-            # this helper to make sure the `send_event` calls actually run.
+            # Some `send_event_rollback_unsafe` calls need to be executed only after the
+            # current transaction commits (using `on_commit` hooks). Because the transaction
+            # in Django tests never commits (rather, gets rolled back after the test completes),
+            # such events would never be sent in tests, and we would be unable to verify them.
+            # Hence, we use this helper to make sure the `send_event_rollback_unsafe` calls actually run.
             self.captureOnCommitCallbacks(execute=True),
         ):
             yield lst