chg: dev: Improve C23 compatibility

Use C23 stdckdint.h when available and define ckd_{mul,add,sub} shims to __builtin_{mul,add,sub}_overflow(). Require all the __builtin functions to be supported to further simplify the non-C23 implementation.  Rename the <stdbit.h>-shims in <isc/bit.h> to their C23 names.

Merge branch 'ondrej/use-stdckdint.h-if-available' into 'main'

See merge request isc-projects/bind9!10818