RFR: 8237505: RadioMenuItem in ToggleGroup: deselected on accelerator [v2]

[Karthik P K]

> No check was present in `RadioMenuItem` accelerator to see if it is in a `ToggleGroup` or not.
> 
> Made changes to check if `RadioMenuItem` is part of `ToggleGroup` or not. If it is part of a `ToggleGroup`, then it can not be cleared using accelerator.
> 
> Added test to validate the change.

Karthik P K has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1002/files
  - new: https://git.openjdk.org/jfx/pull/1002/files/b124c24e..42e8c397

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1002&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1002&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jfx/pull/1002.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/1002/head:pull/1002

PR: https://git.openjdk.org/jfx/pull/1002