Signed-off-by: Mathieu Velten <mathieuv@matrix.org>

Refactor how the `EventContext` class works, with the intention of reducing the amount of state we fetch from the DB during event processing.

The idea here is to get rid of the cached `current_state_ids` and `prev_state_ids` that live in the `EventContext`, and instead defer straight to the database (and its caching). 

One change that may have a noticeable effect is that we now no longer prefill the `get_current_state_ids` cache on a state change. However, that query is relatively light, since its just a case of reading a table from the DB (unlike fetching state at an event which is more heavyweight). For deployments with workers this cache isn't even used.


Part of #12684

There are a bunch of places we call get_success on an immediate value, which is unnecessary. Let's rip them out, and remove the redundant functionality in get_success and friends.

The intention here is to avoid doing state lookups for outliers in
`/_matrix/federation/v1/event`. Unfortunately that's expanded into something of
a rewrite of `filter_events_for_server`, which ended up trying to do that
operation in a couple of places.

Avoid trying to get the state for outliers, which isn't a sensible thing to do.

The presence of this method was confusing, and mostly present for backwards
compatibility. Let's get rid of it.

Part of #11733

This reverts commit 158d73eb.

Revert "Sort internal changes in changelog"
Revert "Update CHANGES.md"
Revert "1.49.0rc1"
Revert "Revert "Move `glob_to_regex` and `re_word_boundary` to `matrix-python-common` (#11505) (#11527)"
Revert "Refactors in `_generate_sync_entry_for_rooms` (#11515)"
Revert "Correctly register shutdown handler for presence workers (#11518)"
Revert "Fix `ModuleApi.looping_background_call` for non-async functions (#11524)"
Revert "Fix 'delete room' admin api to work on incomplete rooms (#11523)"
Revert "Correctly ignore invites from ignored users (#11511)"
Revert "Fix the test breakage introduced by #11435 as a result of concurrent PRs (#11522)"
Revert "Stabilise support for MSC2918 refresh tokens as they have now been merged into the Matrix specification. (#11435)"
Revert "Save the OIDC session ID (sid) with the device on login (#11482)"
Revert "Add admin API to get some information about federation status (#11407)"
Revert "Include bundled aggregations in /sync and related fixes (#11478)"
Revert "Move `glob_to_regex` and `re_word_boundary` to `matrix-python-common` (#11505)"
Revert "Update backward extremity docs to make it clear that it does not indicate whether we have fetched an events' `prev_events` (#11469)"
Revert "Support configuring the lifetime of non-refreshable access tokens separately to refreshable access tokens. (#11445)"
Revert "Add type hints to `synapse/tests/rest/admin` (#11501)"
Revert "Revert accidental commits to develop."
Revert "Newsfile"
Revert "Give `tests.server.setup_test_homeserver` (nominally!) the same behaviour"
Revert "Move `tests.utils.setup_test_homeserver` to `tests.server`"
Revert "Convert one of the `setup_test_homeserver`s to `make_test_homeserver_synchronous`"
Revert "Disambiguate queries on `state_key` (#11497)"
Revert "Comments on the /sync tentacles (#11494)"
Revert "Clean up tests.storage.test_appservice (#11492)"
Revert "Clean up `tests.storage.test_main` to remove use of legacy code. (#11493)"
Revert "Clean up `tests.test_visibility` to remove legacy code. (#11495)"
Revert "Minor cleanup on recently ported doc pages  (#11466)"
Revert "Add most of the missing type hints to `synapse.federation`. (#11483)"
Revert "Avoid waiting for zombie processes in `synctl stop` (#11490)"
Revert "Fix media repository failing when media store path contains symlinks (#11446)"
Revert "Add type annotations to `tests.storage.test_appservice`. (#11488)"
Revert "`scripts-dev/sign_json`: support for signing events (#11486)"
Revert "Add MSC3030 experimental client and federation API endpoints to get the closest event to a given timestamp (#9445)"
Revert "Port wiki pages to documentation website (#11402)"
Revert "Add a license header and comment. (#11479)"
Revert "Clean-up get_version_string (#11468)"
Revert "Link background update controller docs to summary (#11475)"
Revert "Additional type hints for config module. (#11465)"
Revert "Register the login redirect endpoint for v3. (#11451)"
Revert "Update openid.md"
Revert "Remove mention of OIDC certification from Dex (#11470)"
Revert "Add a note about huge pages to our Postgres doc (#11467)"
Revert "Don't start Synapse master process if `worker_app` is set (#11416)"
Revert "Expose worker & homeserver as entrypoints in `setup.py` (#11449)"
Revert "Bundle relations of relations into the `/relations` result. (#11284)"
Revert "Fix `LruCache` corruption bug with a `size_callback` that can return 0 (#11454)"
Revert "Eliminate a few `Any`s in `LruCache` type hints (#11453)"
Revert "Remove unnecessary `json.dumps` from `tests.rest.admin` (#11461)"
Revert "Merge branch 'master' into develop"

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changes made to e713855d.

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>

Collect all the things that make room-versions different to one another into
one place, so that it's easier to define new room versions.

for easier unit testing.