[jdk17u-dev] RFR: 8323717: Introduce test keyword for tests that need external dependencies [v2]

[Aleksey Shipilev]

> Semi-clean backport to allow running all tests cleanly. There was a contextual conflict in `TEST.ROOT` due to the absence of [JDK-8317228](https://bugs.openjdk.org/browse/JDK-8317228) in 17u, which I think can be backported and resolved later.
> 
> Additional testing:
>  - [x] `applications/jcstress applications/scimark` are now properly skipped with `JTREG_KEYWORDS=!external-dep`

Aleksey Shipilev has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Backport 12b89cd2eeb5c2c43a2ce425c96fc4f718e30514

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Changes:
  - all: https://git.openjdk.org/jdk17u-dev/pull/2236/files
  - new: https://git.openjdk.org/jdk17u-dev/pull/2236/files/1fcf983c..e4e14a53

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2236&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2236&range=00-01

  Stats: 66 lines in 32 files changed: 31 ins; 5 del; 30 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2236.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2236/head:pull/2236

PR: https://git.openjdk.org/jdk17u-dev/pull/2236