[jdk11u-dev] RFR: 8210665: Clean up JNI_ENV_ARG and factorize the macros for vmTestbase/jvmti[R-U] tests

[Goetz Lindenmaier]

I backport this for parity with 11.0.14-oracle.

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Commit messages:
 - Backport 85b57de9cebe7eec615ed05710e5d3a6c6b8c430

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/646/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=646&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8210665
  Stats: 1283 lines in 50 files changed: 0 ins; 1019 del; 264 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/646.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/646/head:pull/646

PR: https://git.openjdk.java.net/jdk11u-dev/pull/646