- Remove the requirement for a specific version of Python
- Move dep comment to a separate line, Tox 3.7.0 like trailing ones

Signed-off-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>

State res v2 across large data sets can be very CPU intensive, and if
all the relevant events are in the cache the algorithm will run from
start to finish within a single reactor tick. This can result in
blocking the reactor tick for several seconds, which can have major
repercussions on other requests.

To fix this we simply add the occaisonal `sleep(0)` during iterations to
yield execution until the next reactor tick. The aim is to only do this
for large data sets so that we don't impact otherwise quick resolutions.=

HTTP requires the response to contain a Content-Length header unless chunked encoding is being used.
Prometheus metrics endpoint did not set this, causing software such as prometheus-proxy to not be able to scrape synapse for metrics.

Signed-off-by: Christian Svensson <blue@cmd.nu>

Fix unread counts in sync

Older versions of `parameterized` package have no `parameterized_class` decorator. This decorator is used in tests.

Signed-off-by: Oleg Girko <ol@infoserver.lv>

* Always return an unread_count in get_unread_event_push_actions_by_room_for_user
* Don't always expect unread_count to be there so we don't take out sync entirely if something goes wrong

This requires a new config option to specify which media repo should be
responsible for running background jobs to e.g. clear out expired URL
preview caches.

Implementation of https://github.com/matrix-org/matrix-doc/pull/2625

The aim here is to make it easier to reason about when streams are limited and when they're not, by moving the logic into the database functions themselves. This should mean we can kill of `db_query_to_update_function` function.

This ended up being a bit more invasive than I'd hoped for (not helped by
generic_worker duplicating some of the code from homeserver), but hopefully
it's an improvement.

The idea is that, rather than storing unstructured `dict`s in the config for
the listener configurations, we instead parse it into a structured
`ListenerConfig` object.

Fixes https://github.com/matrix-org/synapse/issues/7683

Broke in: #7649

We had a `yield` acting on a coroutine. To be fair this one is a bit difficult to notice as there's a function in the middle that just passes the coroutine along.