Since #337 it's possible to update the runtime version and metadata. However, that currently needs to be done manually by the user. The way I'd imagine it, is that one listens to runtime upgrade events and then calls the update_runtime function.

This could be offered as a subscription function by the client itself, such that not every user needs to self-implement this.

Open question: Since we'd introduce mulithreading here, is a lock required? If so, is that possible in a no_std environment?