btrfs: test if the capability is kept on incremental send

btrfs: test if the capability is kept on incremental send

This test exercises full send and incremental send operations for cases
where files have capabilities, ensuring the capabilities aren't lost in
the process.

There was a problem with kernel <=5.7 that was making capabilities
to be lost after a combination of full + incremental send. This
behavior was fixed by commit 89efda52e6b6 ("btrfs: send: emit file
capabilities after chown").

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>