RFR: 8253750: use build-stable default seed for Utils.RANDOM_GENERATOR

[Igor Ignatyev]

Hi all,

could you please review the patch which updates `jdk.test.lib.Utils` to use md5 hash-sum of `java.vm.version` property
as default seed for `Utils.RANDOM_GENERATOR`?

from JBS:
> using the same seed for all runs of a build will make it possible (easier) to compare results from different test runs
> (e.g. on different platforms, w/ different flags) and consequently will make test results analysis easier.

the patch also updates `RandomGeneratorTest` test, so it expects now that the same values are generated if no seed is
provided.

testing: ✅ tier1

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Commit messages:
 - 8253750: use build-stable default seed for Utils.RANDOM_GENERATOR

Changes: https://git.openjdk.java.net/jdk/pull/391/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=391&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253750
  Stats: 34 lines in 2 files changed: 26 ins; 6 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/391.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/391/head:pull/391

PR: https://git.openjdk.java.net/jdk/pull/391