RFR: 8179918: EnumSet spliterator should report SORTED, ORDERED, NONNULL [v5]

[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 refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Check for SIZED / SUBSIZED and absence of other flags

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28568/files
  - new: https://git.openjdk.org/jdk/pull/28568/files/5750b26a..bcc973eb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28568&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28568&range=03-04

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 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