RFR: 8304831: TextFlow.hitTest.insertionIndex incorrect with surrogate pairs [v6]

[Karthik P K]

On Thu, 18 May 2023 17:03:53 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

> please try adding firePulse(), and also please check on Windows and Linux. thanks!

I have run the tests in windows and linux. In windows, the red heart emoji which is not a surrogate pair and represented by value 10084 gets displayed along with a box next to it as shown in the picture below.
![image](https://github.com/openjdk/jfx/assets/26969459/f7d9c1f9-69b4-4c7e-aaf0-9464c24d3d3d)

Because of this 2 tests fail. I'm not really sure why the box gets displayed along with the emoji. Red heart emoji inserted in windows using Win key + . also gets displayed in the same way. Am I missing something here? 
`testTextFlowInsertionIndexUsingMultipleEmojis()` test fails sometime because of timing issue which is similar to MacOS.

In Linux all the tests run successfully.

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PR Comment: https://git.openjdk.org/jfx/pull/1091#issuecomment-1554435337