* bump defmt to v0.3
remove Cargo features which are no longer needed
* remove `timestamp!`
it's no longer mandatory and a monotonic counter does not add much value given that `defmt-rtt`
works by disabling interrupts so one won't see logs out of order anyways (which would the case for a
lock-free multi-channel `Logger`)
* use println! in most the examples
so that all examples print something when `DEFMT_LOG` is unset
* make overflow example terminate in less steps
also include an estimate of the stack pointer to show the stack grows downwards towards the RAM
boundary
Jorge AparicioandGitHub