I was trying to understand how `cachedList` works, and ended up writing this
extra test. I figure we may as well keep it.

This PR is tantamount to running:

    python3.8 -m com2ann -v 6 tests/

(com2ann requires python 3.8 to run)

This is the first of two PRs which seek to address #8518. This first PR lays the groundwork by extending ResponseCache; a second PR (#10158) will update the SyncHandler to actually use it, and fix the bug.

The idea here is that we allow the callback given to ResponseCache.wrap to decide whether its result should be cached or not. We do that by (optionally) passing a ResponseCacheContext into it, which it can modify.

Fixes #10068

* Make `invalidate` and `invalidate_many` do the same thing

... so that we can do either over the invalidation replication stream, and also
because they always confused me a bit.

* Kill off `invalidate_many`

* changelog

`keylen` seems to be a thing that is frequently incorrectly set, and we don't really need it.

The only time it was used was to figure out if we had removed a subtree in `del_multi`, which we can do better by changing `TreeCache.pop` to return a different type (`TreeCacheNode`).

Commits should be independently reviewable.

- use a tuple rather than a list for the iterable that is passed into the
  wrapped function, for performance

- test that we can pass an iterable and that keys are correctly deduped.

* tests for push rule pattern matching

* tests for acl pattern matching

* factor out common `re.escape`

* Factor out common re.compile

* Factor out common anchoring code

* add word_boundary support to `glob_to_regex`

* Use `glob_to_regex` in push rule evaluator

NB that this drops support for character classes. I don't think anyone ever
used them.

* Improve efficiency of globs with multiple wildcards

The idea here is that we compress multiple `*` globs into a single `.*`. We
also need to consider `?`, since `*?*` is as hard to implement efficiently as
`**`.

* add assertion on regex pattern

* Fix mypy

* Simplify glob_to_regex

* Inline the glob_to_regex helper function

Signed-off-by: Dan Callahan <danc@element.io>

* Moar comments

Signed-off-by: Dan Callahan <danc@element.io>

Co-authored-by: Dan Callahan <danc@element.io>

As far as I can tell our logging contexts are meant to log the request ID, or sometimes the request ID followed by a suffix (this is generally stored in the name field of LoggingContext). There's also code to log the name@memory location, but I'm not sure this is ever used.

This simplifies the code paths to require every logging context to have a name and use that in logging. For sub-contexts (created via nested_logging_contexts, defer_to_threadpool, Measure) we use the current context's str (which becomes their name or the string "sentinel") and then potentially modify that (e.g. add a suffix).

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;`>

Part of #9366

Adds in fixes for B006 and B008, both relating to mutable parameter lint errors.

Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>

Records additional request information into the structured logs,
e.g. the requester, IP address, etc.

 - Update black version to the latest
 - Run black auto formatting over the codebase
    - Run autoformatting according to [`docs/code_style.md
`](https://github.com/matrix-org/synapse/blob/80d6dc9783aa80886a133756028984dbf8920168/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version

Ensure that we lock correctly to prevent multiple concurrent metadata load
requests, and generally clean up the way we construct the metadata cache.

We passed in a graph to `sorted_topologically` which didn't have an
entry for each node (as we dropped nodes with no edges).

We don't always need the full power of a DeferredCache.

We need to make sure we are readu for the `set_cache_factor` callback.

* Add `DeferredCache.get_immediate` method

A bunch of things that are currently calling `DeferredCache.get` are only
really interested in the result if it's completed. We can optimise and simplify
this case.

* Remove unused 'default' parameter to DeferredCache.get()

* another get_immediate instance

rather than have everything that instantiates an LruCache manage metrics
separately, have LruCache do it itself.