CLEANUP: debug: make the BUG_ON() macros check the condition in the outer one

CLEANUP: debug: make the BUG_ON() macros check the condition in the outer one

The BUG_ON() macros are made of two levels so as to resolve the condition
to a string. However this doesn't offer much flexibility for performing
other operations when the condition is validated, so let's adjust them so
that the condition is checked in the outer macro and the operations are
performed in the inner one.