StreamChangeCache.get_all_changed_entities incorrect usage

[clokep]

The get_all_changed_entities returns None in the case that the cache cannot provide information on the given stream ordering. Some of the callers treat None equivalent to [] (which corresponds to no changes).

Callers, checked do it correctly. Unchecked are either incorrect or maybe incorrect:

• PresenceEventSource.get_new_events
• PresenceEventSource._filter_all_presence_updates_for_user
• TypingWriterHandler.get_all_typing_updates
• DeviceWorkerStore.get_cached_device_list_changes:
  • SyncHandler._generate_sync_entry_for_device_list
• DeviceWorkerStore.get_users_whose_devices_changed (I'm fairly certain this is incorrect.)
• StreamChangeCache.get_entities_changed

[clokep]

I think user impact would be missed presence updates and missed device change notifications?

[clokep]

Tangentially related to #14435.

[clokep]

I think in both these situations we need to pull the full list of user IDs from the database.