ci: Add tests::uses_selinux tag

[nhosoi]

Enhancement:
Set tests::uses_selinux tag to the test playbook that uses the
selinux role, one of the selinux modules or commands internally.

Reason:
We are improving tox-lsr runcontainer.sh that runs CI tests using a container. (See also https://github.com/richm/tox-lsr/tree/container-improvements.) In the effort, we need a mechanism to skip a test that depends on SELinux since SELinux is disabled in a container, by default.

Result:
This is a sample command line to run all the runnable CI tests using runcontainer.sh in tox-lsr.

tox -e container-ansible-core-2.15 -- --erase-old-snapshot --extra-rpm diffutils \
--extra-skip-tag "tests::uses_selinux" --parallel 4 \
--image-name centos-9 tests/tests_*.yml

As shown in the command line, by passing --extra-skip-tag tests::uses_selinux, the tests tests_basics_files.yml, tests_ovirt_elasticsearch.yml, and tests_relp.yml will be skipped and the series of the tests pass.