RFR: 8283404: [macos] a11y : Screen magnifier does not show JMenu name [v2]

[Abhishek Kumar]

> It seems that the accessibility role returned by the MenuAccessibility class is not correct for top level menu.
> 
> Added a condition check to return the accessibility role as `NSAccessibilityMenuBarItemRole` in stead of `NSAccessibilityMenuRole` for top level menu whose parent is `menubar`. 
> 
> The solution works correctly for screen magnifier as well as voice over. 
> 
> A manual test case is added to verify the fix.
> 
> Note: Tried implementing few a11y methods to fix but for top level menu with `NSAccessibilityMenuRole` doesn't return the a11y label.

Abhishek Kumar has updated the pull request incrementally with one additional commit since the last revision:

  Test instruction update

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13271/files
  - new: https://git.openjdk.org/jdk/pull/13271/files/3c668b46..5a4972aa

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13271&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13271&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13271.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13271/head:pull/13271

PR: https://git.openjdk.org/jdk/pull/13271