testing/trace-cmd: new package

See: https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/about/

As commented in the APKBUILD tests are skipped because they would need to run as root (they try to run actual traces and fail if they can't). Is there a recommended way to handle that, e.g. running the tests in a VM? I have tested the resulting package, but actually running tests in the build would be preferable.