Add proper hardfaults handlers
Right now, we don't deal well with hardfaults:
- Epicardium just becomes unresponsive and at some point the watchdog kicks in.
epic_exit()s with ret-code 255 which will at least be logged to the console but no user feed-back nor a stacktrace either.
- l0dables don't have any handling by default.
MR !79 (closed) has a basic implementation of a HardFault handler which could be repurposed for this in tandem with the new