[jdk21u-dev] RFR: 8340398: [JVMCI] Unintuitive behavior of UseJVMCICompiler option

[Todd V. Jonker]

Clean backport of patch authored by @tzezula and approved by @dougxc

The patch default-enables `useJVMCINativeLibrary` when `EnableJVMCI` is on and `libgraal` present. While this is a behavior change, it seems unlikely that users would deploy `libgraal` and _not_ want it used by JVMCI.

This streamlines configuration of our JDK+Graal distro, which in turn allows two failing tests to pass without modification. 

Equivalent backport to 23: https://github.com/openjdk/jdk23u/pull/136

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Commit messages:
 - Backport 4cd8c75a55163be33917b1fba9f360ea816f3aa9

Changes: https://git.openjdk.org/jdk21u-dev/pull/1024/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1024&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340398
  Stats: 21 lines in 3 files changed: 12 ins; 3 del; 6 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1024.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1024/head:pull/1024

PR: https://git.openjdk.org/jdk21u-dev/pull/1024