Consider logging InvocationId using Display instead of Debug

[tillrohrmann]

In the debug log output of the state machine commands, we seem to be logging the command via Debug. This has the effect that InvocationId is logged the following way:

restate.state_machine.command: InvokerEffect(Effect { invocation_id: InvocationId { partition_key: 2691971143059952921, inner: InvocationUuid(2105477499437878611799103406223967318) }, kind: Failed(InvocationError { code: 409 Aborted, message: "killed", stacktrace: None }) }) 

I think it would be more helpful to use the Display implementation of InvocationId, because then it would have the form inv_12dw5UBHriBL2DJ0pgfNmE46yAptW2rrMJ and would be searchable and easier to correlate with other log statements.

cc @slinkydeveloper