New tests for prior memory protections (EXEC_RODATA), new tests for upcoming
kernel self-protections (USERCOPY_HEAP_SIZE_TO, USERCOPY_HEAP_SIZE_FROM,
USERCOPY_HEAP_FLAG_TO, USERCOPY_HEAP_FLAG_FROM, USERCOPY_STACK_FRAME_TO,
USERCOPY_STACK_FRAME_FROM, USERCOPY_STACK_BEYOND), and updated tests
(ATOMIC_UNDERFLOW, ATOMIC_OVERFLOW).