RFR: 8317358: G1: Make TestMaxNewSize use createTestJvm

[Leo Korinth]

In addition remove deprecated `Long(long)` constructor and rewrite `compareTo` to use `> 0` instead of `== 1`.

Also remove unused `isRunningG1(String[] args)` and `checkIncompatibleNewSize(String[] flags)`

Minimal testing completed, will run tier testing before pushing.

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Commit messages:
 - 8317358: G1: Make TestMaxNewSize use createTestJvm

Changes: https://git.openjdk.org/jdk/pull/16012/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16012&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317358
  Stats: 30 lines in 1 file changed: 0 ins; 23 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/16012.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16012/head:pull/16012

PR: https://git.openjdk.org/jdk/pull/16012