badge23: use delays instead of timers for io tasks

Having lurked some FreeRTOS forum threads, it seems like this is
preferable to the previous approach (timer unblocking a thread using a
queue/semaphore), as it's less resource-intense and doesn't cause a
global timer pileup if one of the tasks causes backpressure.

This is a random commit that might help us chase out Core 0 WDT
interrupts.

Tested on p3.