RFR: 8311946: add support for libgraal specific jtreg tests [v4]

[Doug Simon]

> This PR adds support for `jdk.hasLibgraal` and `vm.libgraal.enabled` properties that can be used with the jtreg `@requires` tag to determine if a libgraal specific test should run.
> 
> * `jdk.hasLibgraal`: the libgraal shared library file is present
> * `vm.libgraal.enabled`: libgraal is used as JIT compiler

Doug Simon has updated the pull request incrementally with three additional commits since the last revision:

 - rename vm.hasLibgraal to jdk.hasLibgraal
 - rename vm.libgraal to vm.hasLibgraal
 - fix indentation

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/14851/files
  - new: https://git.openjdk.org/jdk/pull/14851/files/ce7c1cba..05760ec3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14851&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14851&range=02-03

  Stats: 9 lines in 3 files changed: 0 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/14851.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14851/head:pull/14851

PR: https://git.openjdk.org/jdk/pull/14851