When LocoNet bus is unresponsive, sending to it causes everything to lag due to sending retries

[positron96]

When LocoNet is unresponsive (testing on a bare MCU, disabled LocoNet pullups etc), sending to the bus blocks the thread that initiated the sending., e.g. LocoNetTCPServer or main one (executing CommandStation code).

Partly caused by positron96/LocoNet2#1, but in general retrying sending for some time will block even after that is fixed.
Probably sending should be put into its own thread