Unify the separate testsuites for hpc

For some weird historical reason the testsuite for program coverage is distributed between libraries/hpc/tests andtestsuite/tests/hpc. There is no good rationale for this split, afaik. I think the libraries/hpc/tests suite was implemented first, and testsuite/tests/hpc only contains regression tests which were added later. It would make a lot of sense to completely remove the tests from libraries/hpc and add them to the other tests in testsuite/tests/hpc. Especially because these tests are all integration tests which also test the hpc-binary, so they should not be defined in the hpc library which is completely separate from the binary.