make test should report only on executed tests

This should help to speed up tests significantly. Currently, if we run "make test" with a subset of tests, JTReg would still read the entirety of test root to report on tests that were not run. Even with current suite of tests it gets expensive. If you add more tests to suite -- for example, mounting a large test archive like pre-generated fuzzer tests -- it starts to take a lot of time.

We might default to `-report:executed`. My own CI -- that has millions of tests mounted in `test/` -- was running with `JTREG="OPTIONS=-report:executed"` for years now. I think that should be the default way to run the tests in JDK tree.

There is a wrinkle with jtreg retries: we need to collate together the reports for successful retries from multiple runs. Fortunately, we can then fall back to `-report:all-executed`. CODETOOLS-7903323 is poised to provide a new reporting option, `-report:files`, which would make this whole business easier, we can upgrade to it once minimum jtreg version is bumped. This RFE provides faster tests today, and is backportable to update releases.