landlock: Improve bit operations in audit code

Use the BIT() and BIT_ULL() macros in the new audit code instead of
explicit shifts to improve readability.  Use bitmask instead of modulo
operation to simplify code.

Add test_range1_rand15() and test_range2_rand15() KUnit tests to improve
get_id_range() coverage.

Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Link: https://lore.kernel.org/r/20250512093732.1408485-1-mic@digikod.net


Signed-off-by: Mickaël Salaün <mic@digikod.net>