* Declare new config
* Parse new config
* Read new config
* Don't use trial/our TestCase where it's not needed
Before:
```
$ time trial tests/events/test_utils.py > /dev/null
real 0m2.277s
user 0m2.186s
sys 0m0.083s
```
After:
```
$ time trial tests/events/test_utils.py > /dev/null
real 0m0.566s
user 0m0.508s
sys 0m0.056s
```
* Helper to upsert to event fields
without exceeding size limits.
* Use helper when adding invite/knock state
Now that we allow admins to include events in prejoin room state with
arbitrary state keys, be a good Matrix citizen and ensure they don't
accidentally create an oversized event.
* Changelog
* Move StateFilter tests
should have done this in #14668
* Add extra methods to StateFilter
* Use StateFilter
* Ensure test file enforces typed defs; alphabetise
* Workaround surprising get_current_state_ids
* Whoops, fix mypy
