Supports hard and soft interrupts. In the current implementation, soft
interrupt callbacks will only be called when the VM is executing, ie they
will not be called during a blocking kernel call like k_msleep. And the
behaviour of hard interrupt callbacks will depend on the underlying device,
as well as the amount of ISR stack space.
Soft and hard interrupts tested on frdm_k64f and nucleo_f767zi boards.
Signed-off-by: Damien George <damien@micropython.org>