Add a stand-alone run-tests script to webkitscmpy that runs webkitscmpy tests without relying on webkitpy's harness.
<rdar://problem/111705506>
Pull request: https://github.com/WebKit/WebKit/pull/15514
Committed 265853@main (0de19285caf3): <https://commits.webkit.org/265853@main> Reviewed commits have been landed. Closing PR #15514 and removing active labels.