RFR: 8179918: EnumSet spliterator should report SORTED, ORDERED, NONNULL [v3]

[Patrick Strawderman]

> I noticed that the Spliterator for EnumSet does not report SORTED, ORDERED, or NONNULL characteristics, all of which are inherent to API of EnumSet. I found there's an existing ticket for this as well.
> 
> The ticket also mentions optimized `forEach`, etc, which I presume means avoiding the default implementation that uses the iterator and just iterating over the bitset directly; I can add that here or perhaps in a follow up if it's still deemed worthwhile.

Patrick Strawderman has updated the pull request incrementally with one additional commit since the last revision:

  Add unit test

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28568/files
  - new: https://git.openjdk.org/jdk/pull/28568/files/bbce28c3..9e7a1c50

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28568&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28568&range=01-02

  Stats: 81 lines in 1 file changed: 81 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28568.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28568/head:pull/28568

PR: https://git.openjdk.org/jdk/pull/28568