RFR: 8323717: Introduce test keyword for tests that need external dependencies

[Aleksey Shipilev]

Some jtreg tests require resolvable external dependencies. This resolution is delegated to JIB, which is not used in vanilla OpenJDK testing. It would be convenient to add a keyword that marks tests that require these external dependencies, so that we could exclude those tests from runs. This would allow us to run all tests in hotspot:tier4, which now excludes `applications/` specifically.

I provisionally call this flag `external-dep`, but I am open for other suggestions.

Note that some tests that pull `@Artifact`-s provide special paths that do limited testing anyway. However, there are tests which cannot run without external dependencies at all. These include at least `applications/jcstress` and `applications/scimark` tests.

Ironically, I cannot run the jcstress test generator because the dependencies are lacking here. I regenerated those test using a self-built jcstress 0.16 bundle.

Additional testing:
 - [x] `make test TEST=applications/` fails
 - [x]  `JTREG_KEYWORDS=!external-dep make test TEST=applications/` passes, skipping most of the tests

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Commit messages:
 - Initial work

Changes: https://git.openjdk.org/jdk/pull/17421/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17421&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323717
  Stats: 62 lines in 32 files changed: 32 ins; 0 del; 30 mod
  Patch: https://git.openjdk.org/jdk/pull/17421.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17421/head:pull/17421

PR: https://git.openjdk.org/jdk/pull/17421