feat: Do direct ssh when using an rv

[XavierChanth]

Sshnp no double ssh option - as we have the rv we do not have to double ssh. Option shpuld still be there and only used if needed. I.E. a direct connectoon (-h with no @)

Tasks

Beta Give feedback

1. Design Spike implementation to prove it
2. daemon Refactor to cleanly separate new request notification handling from previous versions and allow the relevant code to be fully reused
3. daemon Implement stub handler for new request notification
4. daemon Implement full handler for new request notification format where double ssh is requested, to prove backwards compatibility
5. daemon Implement full handler for new request notification format where direct ssh is requested
6. client Refactor to clearly separate new request notification sending from previous versions while allowing reusability
7. client Add a version check to determine whether to use new or legacy request notification format30m
8. client Implement new request sender
9. Test Augment end-to-end tests to cover both direct ssh and double ssh

[gkc]

Spiked at the weekend and got this working albeit resulted in a bunch of bug-prone hard-to-grok difficult-to-maintain code. See plan in issue description above

[gkc]

This is complete except for the last task (Augment end-to-end tests to cover both direct ssh and double ssh) which is also covered in the release 4.0.0 tracker, so will close this ticket as completed.