[jdk11u-dev] RFR: 8256110: Create implementation for NSAccessibilityStepper protocol

[Autumn Capasso]

Clean backport for oracle parity.

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Commit messages:
 - Backport 5dc5d9401e7a176da53a14293fb59e97b644b31a

Changes: https://git.openjdk.org/jdk11u-dev/pull/1596/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1596&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8256110
  Stats: 131 lines in 5 files changed: 114 ins; 15 del; 2 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1596.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1596/head:pull/1596

PR: https://git.openjdk.org/jdk11u-dev/pull/1596