RFR: 8264293: Create implementation for NSAccessibilityMenu protocol peer

[Alexander Zuev]

Added implementation for all menu related protocol peers;
Native methods moved to CommonComponentAccessibility so they are called on correct peers;

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Commit messages:
 - 8264293: Create implementation for NSAccessibilityMenu protocol peer

Changes: https://git.openjdk.java.net/jdk/pull/6421/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6421&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264293
  Stats: 356 lines in 8 files changed: 308 ins; 48 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6421.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6421/head:pull/6421

PR: https://git.openjdk.java.net/jdk/pull/6421