RFR: 8296275: Write a test to verify setAccelerator method of JMenuItem.

[Naveen Narayanan]

Colocate JMenuItemSetAcceleratorTest to a regression test.

This testcase will
1) Verify setAccelerator method of JMenuitem.
2) Check that the selection of a menu item in the menu bar will generate action by a key combination of META+M.

Testing:
Tested using Mach5(20 times per platform) in Mac OS, Linux and Windows and got all pass.

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

Commit messages:
 - 8296275: Write a test to verify setAccelerator method of JMenuItem.

Changes: https://git.openjdk.org/jdk/pull/11035/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11035&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296275
  Stats: 89 lines in 1 file changed: 89 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11035.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11035/head:pull/11035

PR: https://git.openjdk.org/jdk/pull/11035