printf: break kunit into test cases

Move all tests into `printf_test_cases`. This gives us nicer output in
the event of a failure.

Combine `plain_format` and `plain_hash` into `hash_pointer` since
they're testing the same scenario.

Signed-off-by: Tamir Duberstein <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Tested-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Kees Cook <[email protected]>

Author: tamird