Make validy lemmas for `excl_auth` more consistent with `auth`.

- Rename `excl_auth_frag_validN_op_1_l` into `excl_auth_frag_op_validN` and
  `excl_auth_frag_valid_op_1_l` into `excl_auth_frag_op_valid` (similar to
  `auth_auth_op_valid`, and make them bi-implications.
- Add `excl_auth_auth_op_validN` and `excl_auth_auth_op_valid`