RFR: JDK-8311113: Remove invalid pointer cast and clean up setLabel() in awt_MenuItem.cpp [v3]

[Harshitha Onkar]

> In awt_MenuItem.cpp (712,22): ` mii.dwTypeData = (LPTSTR)(*sb)`  produces invalid pointer cast warning when complied on clang and moreover this is a no-op.  
> 
> `mii.dwTypeData` is used only when **MIIM_STRING** flag is set in the fMask (as per [Docs](https://learn.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-menuiteminfoa)), which is not the case in JDK [Ln#705](https://github.com/openjdk/jdk/blob/e56d3bc2dab3d32453b6eda66e8434953c436084/src/java.desktop/windows/native/libawt/windows/awt_MenuItem.cpp#L706). Hence the assignment ` mii.dwTypeData = (LPTSTR)(*sb)`  is not required and so is the label parameter. Additionally necessary cleanup is done at the following places -
> 
> - WMenuItemPeer.java - to the native function call
> - awt_MenuItem.cpp -  `WMenuItemPeer__1setLabel() ,_SetLabel(), SetLabel()`
> - awt_MenuItem.h
> 
> Added a test which checks setLabel() functionality on Menu, MenuItem and PopupMenu.

Harshitha Onkar has updated the pull request incrementally with one additional commit since the last revision:

  removed robot.waitForIdle() calls

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15276/files
  - new: https://git.openjdk.org/jdk/pull/15276/files/c10275c2..47b4a0c6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15276&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15276&range=01-02

  Stats: 39 lines in 1 file changed: 20 ins; 7 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/15276.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15276/head:pull/15276

PR: https://git.openjdk.org/jdk/pull/15276