add new test which covers perf_event class+permissions
    
    The kernel already recognizes the perf_event class and its permissions.
    Current SELinux policy does not, but it will.
    To avoid possible issues, we need to test some basic scenarios which
    take advantage of the perf_event class. For example: the perf tool
    executed by root/unconfined_t user.
    
    The TC covers BZ#1901957.