Requests that modify push rules cannot be routed to workers

[anoadragon453]

#5063 allowed worker processes to service read-only push rule-related endpoints. This is an issue to track the remaining push rule-related endpoints that require writes.

The following endpoints cannot yet be routed to worker processes:

• PUT /_matrix/client/v3/pushrules/{scope}/{kind}/{ruleId}
• DELETE /_matrix/client/v3/pushrules/{scope}/{kind}/{ruleId}
• PUT /_matrix/client/v3/pushrules/{scope}/{kind}/{ruleId}/actions
• PUT /_matrix/client/v3/pushrules/{scope}/{kind}/{ruleId}/enabled

I believe this hinges on converting the push rules stream to use a MultiWriterIdGenerator, instead of what we have today?

synapse/synapse/storage/databases/main/push_rule.py

Lines 132 to 139 in 0d1d3e0

	if hs.config.worker.worker_app is None:
	self._push_rules_stream_id_gen: AbstractStreamIdTracker = StreamIdGenerator(
	db_conn, "push_rules_stream", "stream_id"
	)
	else:
	self._push_rules_stream_id_gen = SlavedIdTracker(
	db_conn, "push_rules_stream", "stream_id"
	)

We did a similar piece of work for moving presence off of the main process.