Fixes matrix-org/complement#330 (or it will, once we remove the old files).

It's not quite a lift-and-shift: I've also taken the opportunity to get rid of the custom CA that we used to use to sign the TLS certs, which has been superceded by the CA exposed by Complement.

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

* Pull out query param types to `synapse.http.types`
* Use QueryParams everywhere
* Simplify `encode_query_args`
* Add annotation which would have caught #12410

Signed-off-by: Jorge Florian <jafn28@gmail.com>

Currently causes future incremental syncs to fail.

Broke by #12191

Broke by #12364

Now that MSC2675 has passed FCP and the implementation is
compliant with the final version.

As discussed at https://github.com/matrix-org/synapse/pull/12179#discussion_r837263852

And update the upgrade notes to point at old versions of the documentation.

Fixes a bug introduced in #11417 where we would only included backfilled events
in `synapse_event_persisted_position`

Principally, `prometheus_client.REGISTRY.register` now requires its argument to
extend `prometheus_client.Collector`.

Additionally, `Gauge.set` is now annotated so that passing `Optional[int]`
causes an error.

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

Update mdbook (the tool used to render the documentation website) to version 0.4.17.

Just after a task acquires a contended `Linearizer` lock, it sleeps.
If the task is cancelled during this sleep, we need to release the lock.

Signed-off-by: Sean Quah <seanq@element.io>

`StreamToken.from_string` and `RoomStreamToken.parse` are both async
methods that could be cancelled. These methods must not replace
`CancelledError`s with `SynapseError`s.

Signed-off-by: Sean Quah <seanq@element.io>

Signed-off-by: Sean Quah <seanq@element.io>

Refactor and convert `Linearizer` to async. This makes a `Linearizer`
cancellation bug easier to fix.

Also refactor to use an async context manager, which eliminates an
unlikely footgun where code that doesn't immediately use the context
manager could forget to release the lock.

Signed-off-by: Sean Quah <seanq@element.io>

Signed-off-by: Sean Quah <seanq@element.io>

Fix a spec compliance issue where requests to the `/publicRooms` federation API would specify `limit` as a string. (#12364)