Fix some harmless errors from background processes (mostly
due to awaiting Mock objects) that occurred in the Synapse
logs during unit tests.

Part of #9744

Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.

`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl&gt;`>

We do it this way round so that only the "owner" can delete the access token (i.e. `/logout/all` by the "owner" also deletes that token, but `/logout/all` by the "target user" doesn't).

A future PR will add an API for creating such a token.

When the target user and authenticated entity are different the `Processed request` log line will be logged with a: `{@admin:server as @bob:server} ...`. I'm not convinced by that format (especially since it adds spaces in there, making it harder to use `cut -d ' '` to chop off the start of log lines). Suggestions welcome.

* Limit AS transactions to 100 events

* Update changelog.d/8606.feature

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

* Add tests

* Update synapse/appservice/scheduler.py

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

Optionally sends typing, presence, and read receipt information to appservices.

Get rid of the labyrinthine `recoverer_fn` code, and clean up the startup code
(it seemed to be previously inexplicably split between
`ApplicationServiceScheduler.start` and `_Recoverer.start`).

Add some docstrings too.

... which were making other, innocent, tests, fail.

Plus remove a spurious unittest.DEBUG which was making the output noisy.

Defaults ID to as_token if not specified. This will change
when IDs are fully supported.

This was caused by not explicitly checking the service.sender field. This
has now been fixed and a regression test has been added.

Replace EventGrouper for ServiceQueuer to move to push-based txns. Fix tests and add stub tests for ServiceQueuer.

With tests to assert behaviour. Not hooked up yet. Stub datastore methods
not implemented yet.