Give sensible names for '_simple_...' transactions

synapse/storage/__init__.py

synapse/storage/_base.py

synapse/storage/directory.py

synapse/storage/filtering.py

synapse/storage/media_repository.py

synapse/storage/presence.py

synapse/storage/profile.py

synapse/storage/push_rule.py

synapse/storage/pusher.py

synapse/storage/registration.py

synapse/storage/rejections.py

synapse/storage/room.py

synapse/storage/roommember.py