* Disable aggregation bundling on `/sync` responses

A partial revert of #11478. This turns out to have had a significant CPU impact
on initial-sync handling. For now, let's disable it, until we find a more
efficient way of achieving this.

* Fix tests.

Co-authored-by: Patrick Cloke <patrickc@matrix.org>

This reverts commit a77c3698.

* Move sync_token up to the top
* Pull out _get_ignored_users
* Try to signpost the body of `_generate_sync_entry_for_rooms`
* Pull out _calculate_user_changes

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

Fixes #11517

After #10847, `looping_background_call` would print an error in the logs
every time a non-async function was called. Since the error would be
caught and ignored immediately, there were no other side effects.

If, for some reason, we don't have the create event, we should still be able to
purge a room.

Stabilise support for MSC2918 refresh tokens as they have now been merged into the Matrix specification. (#11435)

As a step towards allowing back-channel logout for OIDC.

Due to updates to MSC2675 this includes a few fixes:

* Include bundled aggregations for /sync.
* Do not include bundled aggregations for /initialSync and /events.
* Do not bundle aggregations for state events.
* Clarifies comments and variable names.

Update backward extremity docs to make it clear that it does not indicate whether we have fetched an events' `prev_events` (#11469)

Spawning from https://github.com/matrix-org/synapse/pull/9445#discussion_r758958181



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

Support configuring the lifetime of non-refreshable access tokens separately to refreshable access tokens. (#11445)

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>

by calling into `make_test_homeserver_synchronous`.

The function *could* have been inlined at this point but the function is big enough

and it felt fine to leave it as is.

At least there isn't a confusing name clash anymore!

It had no users.

We have just taken the identity of a previous function but don't provide the same
behaviour, so we need to fix this in the next commit...

and pass in the homeserver rather than calling a same-named function to ask for one.

Later commits will jiggle things around to make this sensible.

We're going to add a `state_key` column to the `events` table, so we need to
add some disambiguation to queries which use it.

This mainly consists of docstrings and inline comments. There are one or two type annotations and variable renames thrown in while I was here.

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

* move wiki pages to synapse/docs and add a few titles where necessary

* update SUMMARY.md with added pages

* add changelog

* move incorrectly located newsfragment

* update changelog number

* snake case added files and update summary.md accordingly

* update issue/pr links

* update relative links to docs

* update changelog to indicate that we moved wiki pages to the docs and state reasoning

* requested changes to admin_faq.md

* requested changes to database_maintenance_tools.md

* requested changes to understanding_synapse_through_graphana_graphs.md

* add changelog

* fix leftover merge errata

* fix unwanted changes from merge

* use two spaces between entries

* outdent code blocks

This skips a few methods which are difficult to type.

Add MSC3030 experimental client and federation API endpoints to get the closest event to a given timestamp (#9445)

MSC3030: https://github.com/matrix-org/matrix-doc/pull/3030



Client API endpoint. This will also go and fetch from the federation API endpoint if unable to find an event locally or we found an extremity with possibly a closer event we don't know about.
```
GET /_matrix/client/unstable/org.matrix.msc3030/rooms/<roomID>/timestamp_to_event?ts=<timestamp>&dir=<direction>
{
    "event_id": ...
    "origin_server_ts": ...
}
```

Federation API endpoint:
```
GET /_matrix/federation/unstable/org.matrix.msc3030/timestamp_to_event/<roomID>?ts=<timestamp>&dir=<direction>
{
    "event_id": ...
    "origin_server_ts": ...
}
```

Co-authored-by: Erik Johnston <erik@matrix.org>

* move wiki pages to synapse/docs and add a few titles where necessary

* update SUMMARY.md with added pages

* add changelog

* move incorrectly located newsfragment

* update changelog number

* snake case added files and update summary.md accordingly

* update issue/pr links

* update relative links to docs

* update changelog to indicate that we moved wiki pages to the docs and state reasoning

* revert unintentional change to CHANGES.md

* add link

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

* Update CHANGES.md

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>