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.
• Pycardium 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 panic() functionality.