ci: add a GHAction sending data to Coverity

ci: add a GHAction sending data to Coverity

To get it to work a secret named COVERITY_SCAN_TOKEN should
be added to the util-linux repository:
https://docs.github.com/en/actions/security-guides/encrypted-secrets#creating-encrypted-secrets-for-a-repository

It has to match the util-linux project token, which
can be found at
https://scan.coverity.com/projects/karelzak-util-linux?tab=project_settings

Signed-off-by: Evgeny Vereshchagin <evvers@ya.ru>