RFR: 8253750: use build-stable default seed for Utils.RANDOM_GENERATOR [v2]

[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 proposed
>> solution is to use the seed based on Runtime.version() / "java.vm.version", which are different from build to build, if
>> there is no seed specified by "jdk.test.lib.random.seed" property.
> 
> the patch also updates `RandomGeneratorTest` test, so it expects now that the same values are generated if no seed is
> provided.
> testing: ✅ tier1

Igor Ignatyev has updated the pull request incrementally with one additional commit since the last revision:

  used Runtime.version() instead of ${java.vm.version}
  updated javadoc

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/391/files
  - new: https://git.openjdk.java.net/jdk/pull/391/files/b5437f75..381e14f7

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=391&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=391&range=00-01

  Stats: 10 lines in 1 file changed: 4 ins; 0 del; 6 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