ci: add workflow to check downgrade versions

Tarantool has hardcoded list of versions it can downgrade to. This list
should consist of all the released versions less than Tarantool version.
This workflow helps to make sure we update the list before release.

It is run on pushing release tag to the repo, checks the list and fails
if it misses some released version less than current. In this case we
are supposed to update downgrade list (with required downgrade code) and
update the release tag.

Closes #8319

NO_TEST=ci
NO_CHANGELOG=ci
NO_DOC=ci