sched/debug: Add Kconfig to trigger panics on all 'BUG:' conditions

Introduce CONFIG_PANIC_ON_SCHED_BUG to trigger panics along with all
'BUG:' prints from the scheduler core, even potentially-recoverable
ones such as scheduling while atomic, sleeping from invalid context,
and detection of broken arch topologies.

Change-Id: I5d2f561614604357a2bc7900b047e53b3a0b7c6d
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>