RFR: 8311527: Region.snapInnerSpace*() [v2]

[Andy Goryachev]

> Introduces Region.snapInnerSpaceX/Y() methods for dealing with inner space (using Math.floor), see for instance [JDK-8299753](https://bugs.openjdk.org/browse/JDK-8299753), using existing methods Region.snapPortionX/Y().

Andy Goryachev 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 eight additional commits since the last revision:

 - review comments
 - Merge remote-tracking branch 'origin/master' into ag.8311527.snap.inner
 - tests
 - Merge remote-tracking branch 'origin/master' into ag.8311527.snap.inner
 - javadoc
 - snap portion
 - cleanup
 - 8311527: snap inner space

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1190/files
  - new: https://git.openjdk.org/jfx/pull/1190/files/ee0967f3..790325dd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1190&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1190&range=00-01

  Stats: 549 lines in 31 files changed: 448 ins; 48 del; 53 mod
  Patch: https://git.openjdk.org/jfx/pull/1190.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1190/head:pull/1190

PR: https://git.openjdk.org/jfx/pull/1190