kselftest: Add basic test for probing the rust sample modules

Add new basic kselftest that checks if the available rust sample modules
can be added and removed correctly.

Signed-off-by: Laura Nao <laura.nao@collabora.com>
Reviewed-by: Sergio Gonzalez Collado <sergio.collado@gmail.com>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>