RFR: 8298725: Add BitMap support for reverse iteration [v2]

[Kim Barrett]

> Please review this addition of BitMap::reverse_iterate, which is like
> BitMap::iterate but visits the set bits in a range from high index to low.
> 
> Testing:
> mach5 tier1, which includes running the updated gtests on all Oracle-supported
> platform

Kim Barrett 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 two additional commits since the last revision:

 - Merge branch 'master' into bitmap-rev-iterate
 - add reverse_iterate

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13151/files
  - new: https://git.openjdk.org/jdk/pull/13151/files/d52a34fb..30462f8b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13151&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13151&range=00-01

  Stats: 7411 lines in 158 files changed: 1758 ins; 5049 del; 604 mod
  Patch: https://git.openjdk.org/jdk/pull/13151.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13151/head:pull/13151

PR: https://git.openjdk.org/jdk/pull/13151