[jdk21u-dev] RFR: 8323717: Introduce test keyword for tests that need external dependencies

[Aleksey Shipilev]

Clean backport to make sure we can exclude JIB-managed tests from `all` test runs. GHA would sanity check this PR.

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Commit messages:
 - Backport 12b89cd2eeb5c2c43a2ce425c96fc4f718e30514

Changes: https://git.openjdk.org/jdk21u-dev/pull/262/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=262&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/jdk21u-dev/pull/262.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/262/head:pull/262

PR: https://git.openjdk.org/jdk21u-dev/pull/262