RFR: 8265279: Remove unused RandomGeneratorFactory.all(Class<T> category)

[Jim Laskey]

No longer needed

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Commit messages:
 - RandomGeneratorFactory.all(Class<T> category) no longer needed
 - Remove extraneous references to makeXXXSpliterator
 - Move makeXXXSpliterator methods to RandomSupport
 - change static final from 'proxy' to 'PROXY'
 - Make makeXXXSpliterator final
 - Move makeXXXSpilterator from public (@hidden) to protected. No API change.

Changes: https://git.openjdk.java.net/jdk/pull/3516/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3516&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265279
  Stats: 229 lines in 5 files changed: 19 ins; 184 del; 26 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3516.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3516/head:pull/3516

PR: https://git.openjdk.java.net/jdk/pull/3516