netcheck: Implement https probe
The https probe is currently included in the probeplan and executed, but it is not implemented either as a probe nor in the derper. Both need to be implemented.
https://github.com/n0-computer/iroh/tree/flub/https-probe is a branch where this was implemented fairly fully. It stalled on something silly, I think tests (which now should be possible - there is testing infra to run an entire relay server in a unittest now). It probably can't be merged immediately because so much has changed, but hopefully a lot of it can be used.
This is necessary work for #2799
@flub can this be closed now that https://github.com/n0-computer/iroh/pull/2903 landed?
yes!