- Rename the rotation list to default_encrypt_tables in
fil_system_t. Because rotation list naming could be
misleading when it comes to key version rotation

- Rename is_in_rotation_list to is_in_default_encrypt
in fil_space_t

- Rename keyrotate_next function to default_encrypt_next

fil_system_t::default_encrypt_next(): Find the next
suitable default encrypt table if beginning of
default_encrypt_tables list has been scheduled
to be deleted