bcc/python: Add test_attach_perf_event.py to CMake tests

bcc/python: Add test_attach_perf_event.py to CMake tests

Add to CMakeLists.txt of tests so that the test is run as part of github
actions test suite. Shorten the sleep duration so test finishes faster -
since it's just testing attach currently the extra time isn't producing
more signal.

Also add python equivalent of `perf_event_sample_format` enum so
`sample_type` can be more clearly set.

v2: The test doesn't work on ubuntu 16.04 due to old kernel headers. It
doesn't work on the rest of the github actions VMs due to hardware perf
events not being supported, so add necessary check / skip.