RFR: 8312019: Simplify and modernize java.util.BitSet.equals [v2]

[Pavel Rappo]

> Please review this PR to use modern APIs and language features to simplify equals for BitSet. 
> 
> I couldn't see how to refactor hashCode using Arrays utility methods in a way that preserves its specification. So, aside from refactoring its doc comment and annotating it with `@Overrides`, I left it intact.

Pavel Rappo has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'master' into 8312019
 - Use a leaner utility method
 - Initial commit

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14868/files
  - new: https://git.openjdk.org/jdk/pull/14868/files/39de7d2a..0a3f1d94

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14868&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14868&range=00-01

  Stats: 10505 lines in 327 files changed: 8461 ins; 958 del; 1086 mod
  Patch: https://git.openjdk.org/jdk/pull/14868.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14868/head:pull/14868

PR: https://git.openjdk.org/jdk/pull/14868