Add manage extension

[sosthene-nitrokey]

The management extension adds support for factory-reseting an entire device. It also allows factory resetting another client.

It also allows preserving a set of files when operating a factory reset.

[robin-nitrokey]

One potential issue would be the separation between the privileged manage extension and the other unprivileged extensions. If we grant access to e. g. the chunking extension to a client, we don’t necessarily want it to have access to the manage extension too. But I think we should be able to fix that in the runner by assigning two backend IDs to the staging backend and only dispatching manage requests for one of them, right?