[jdk17u-dev] RFR: 8317218: G1: Make TestG1HeapRegionSize use createTestJvm

[Goetz Lindenmaier]

I backport this to improve testing in 17.

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

Commit messages:
 - Backport 75b37e6d7ec285f1a954f9d5b16bf9e6b642f2fc

Changes: https://git.openjdk.org/jdk17u-dev/pull/2948/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2948&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317218
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2948.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2948/head:pull/2948

PR: https://git.openjdk.org/jdk17u-dev/pull/2948