Previously we had 3 monoliths:
- dendrite-monolith-server
- dendrite-demo-libp2p
- dendritejs
which all had their own of setting up public routes. Factor this
out into a new `setup.Monolith` struct which gets all dependencies
set as fields. This is different to `basecomponent.Base` which
doesn't provide any way to set configured deps (e.g public rooms db)
Part of a larger process to clean up how we initialise Dendrite.
