Broke by #13522

It looks like we have some rules in the DB with a priority class less
than 0 that don't override the base rules. Before these were just
dropped, but #13522 made that a hard error.

Instrument the federation/backfill part of `/messages` so it's easier to follow what's going on in Jaeger when viewing a trace.

Split out from https://github.com/matrix-org/synapse/pull/13440

Follow-up from https://github.com/matrix-org/synapse/pull/13368

Part of https://github.com/matrix-org/synapse/issues/13356

Synapse does not currently support faster room joins on deployments with
workers.

Signed-off-by: Sean Quah <seanq@matrix.org>

Signed-off-by: Dirk Klimpel <dirk@klimpel.org>

This improves load times for push rules:

| Version              | Time per user | Time for 1k users | 
| -------------------- | ------------- | ----------------- |
| Before               |       138 µs  |             138ms |
| Now (with custom)    |       2.11 µs |            2.11ms |
| Now (without custom) |       49.7 ns |           0.05 ms |

This therefore has a large impact on send times for rooms
with large numbers of local users in the room.

Use Pydantic to systematically validate a first batch of endpoints in `synapse.rest.client.account`. (#13188)

Instrument FederationStateIdsServlet - `/state_ids` so it's easier to follow what's going on in Jaeger when viewing a trace.

This reverts commit f383b9b3. Other PRs
were seeing mypy failures that looked to be related to mypy-zope.
Confusingly, we didn't see this on #13521.

Revert this for now and investigate later.

* Clarifies comments.
* Fixes an erroneous comment (about return type) added in #13455
  (ec248132).
* Clarifies the name of a variable.
* Simplifies logic of pulling out the latest join for the requesting user.

Signed-off-by: James Barton <james@neodon.com>

Add note to `redaction_retention_period` documentation mentioning that event purging runs at most every 5m (#13492)

Events can be un-rejected or newly-rejected during resync, so ensure we update
the database and caches when that happens.

Revert 'Remove the unspecced  field in the  response. (#13365)' to give more time for clients to update. (#13501)

* Use literals in place of `HTTPStatus` constants in tests

* newsfile

* code style

* code style

Add some miscellaneous comments to document sync, especially around
`compute_state_delta`.

Signed-off-by: Sean Quah <seanq@matrix.org>

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

```py
@trace
@tag_args
async def get_oldest_event_ids_with_depth_in_room(...)
  ...
```

Before this PR, you would see a warning in the logs and the span was not exported:
```
2022-08-03 19:11:59,383 - synapse.logging.opentracing - 835 - ERROR - GET-0 - @trace may not have wrapped EventFederationWorkerStore.get_oldest_event_ids_with_depth_in_room correctly! The function is not async but returned a coroutine.
```

Replace
- `HTTPStatus.NOT_FOUND`
- `HTTPStatus.FORBIDDEN`
- `HTTPStatus.UNAUTHORIZED`
- `HTTPStatus.CONFLICT`
- `HTTPStatus.CREATED`

Signed-off-by: Dirk Klimpel <dirk@klimpel.org>