Separate the operation in mock/testing mode from the one in production.

[Radu Ometita]

Describe the feature you'd like

Make the distinction between mock and real node operation at type level, or differently than it is done now. I think that if we rethink a bit the way we test the PAB we can do this even without using much type-level trickery.

Maybe sending mocked transactions should be done through the wallet rather than directly, through the node protocol.

See: #243 (comment)

Describe alternatives you've considered

No response