Based on:

 - MSC3575: Sliding Sync (aka Sync v3): matrix-org/matrix-spec-proposals#3575
 - MSC3885: Sliding Sync Extension: To-Device messages: matrix-org/matrix-spec-proposals#3885
 - MSC3884: Sliding Sync Extension: E2EE: matrix-org/matrix-spec-proposals#3884

We were using the enum just to distinguish /sync v2
vs Sliding Sync /sync/e2ee so we should just make an
enum for that instead of trying to glom onto the
existing `sync_type` (overloading it).

See #17167 (comment)
-> https://stackoverflow.com/questions/28333478/python-unittest-testcase-with-inheritance

Conflicts:
	synapse/handlers/sync.py
	tests/handlers/test_sync.py

See #17167 (comment)

See #17167 (comment)

See #17167 (comment)

…mods/msc3575-sliding-sync-0.0.1

See #17167 (comment)

Conflicts:
	synapse/handlers/sync.py

 - Added `room.account_data` and `room.presence` to avoid extra work in `_generate_sync_entry_for_rooms()`
 - Added a comment to the top-level `account_data` and `presence` filters that `(This is just here for good measure)`

See #17167 (comment)

See #17167 (comment)

As suggested in #17167 (comment)

…mods/msc3575-sliding-sync-0.0.1

See #17167 (comment)

See #17167 (comment)

…mods/msc3575-sliding-sync-0.0.1

Conflicts:
	synapse/rest/client/sync.py

See #17187 (comment)

See pydantic/pydantic#156 (comment)

…p for user

Spawning from #17187

Before:
```
$ SYNAPSE_POSTGRES=1 SYNAPSE_POSTGRES_USER=postgres SYNAPSE_TEST_LOG_LEVEL=INFO poetry run trial tests.replication.storage.test_events
[...]
Traceback (most recent call last):
  File "pypoetry/virtualenvs/matrix-synapse-xCtC9ulO-py3.12/lib/python3.12/site-packages/twisted/trial/runner.py", line 711, in loadByName
    return self.suiteFactory([self.findByName(name, recurse=recurse)])
  File "pypoetry/virtualenvs/matrix-synapse-xCtC9ulO-py3.12/lib/python3.12/site-packages/twisted/trial/runner.py", line 474, in findByName
    obj = reflect.namedModule(searchName)
  File "pypoetry/virtualenvs/matrix-synapse-xCtC9ulO-py3.12/lib/python3.12/site-packages/twisted/python/reflect.py", line 156, in namedModule
    topLevel = __import__(name)
  File "synapse/tests/replication/storage/test_events.py", line 33, in <module>
    from synapse.handlers.room import RoomEventSource
  File "synapse/synapse/handlers/room.py", line 74, in <module>
    from synapse.rest.admin._base import assert_user_is_admin
  File "synapse/synapse/rest/__init__.py", line 24, in <module>
    from synapse.rest import admin
  File "synapse/synapse/rest/admin/__init__.py", line 41, in <module>
    from synapse.handlers.pagination import PURGE_HISTORY_ACTION_NAME
  File "synapse/synapse/handlers/pagination.py", line 30, in <module>
    from synapse.handlers.room import ShutdownRoomParams, ShutdownRoomResponse
builtins.ImportError: cannot import name 'ShutdownRoomParams' from partially initialized module 'synapse.handlers.room' (most likely due to a circular import) (synapse/synapse/handlers/room.py)
```

…ods/msc3575-sliding-sync-0.0.1

Conflicts:
	synapse/handlers/initial_sync.py
	tests/replication/storage/test_events.py

Avoid flawed raw stream comparison.