RFR: 8352506: Simplify make/test/JtregNativeHotspot.gmk

[Magnus Ihse Bursie]

The file to setup special arguments to native JTReg Hotspot tests is needlessly complicated. With some generalisation, we can make it much simpler.

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Commit messages:
 - 8352506: Simplify make/test/JtregNativeHotspot.gmk

Changes: https://git.openjdk.org/jdk/pull/24130/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24130&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352506
  Stats: 1527 lines in 2 files changed: 35 ins; 1447 del; 45 mod
  Patch: https://git.openjdk.org/jdk/pull/24130.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24130/head:pull/24130

PR: https://git.openjdk.org/jdk/pull/24130