selftests/fs/mount-notify: build with tools include dir

Copy the fanotify uapi header files to the tools include dir
and define __kernel_fsid_t to decouple dependency with headers_install
and then remove the redundant re-definitions of fanotify macros.

Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/20250509133240.529330-6-amir73il@gmail.com


Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>