RFR: 8314683: TextArea: scroll bar size and content padding

[Kevin Rushforth]

On Fri, 31 May 2024 21:50:08 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

> Changing certain ScrollBar, ScrollPane, and TextArea sizes from `em` to `px` in modena.css to make them independent of the font size *in that control*.
> 
> After the change, the UI still looks good which can be tested by scaling default font size in a fairly wide range:
> 
> 
> .root { -fx-font-size:100%; }
> 
> 
> Using CSS Playground tool in the Monkey Tester at 50% and 200% font size:
> 
> ![Screenshot 2024-05-31 at 14 48 41](https://github.com/openjdk/jfx/assets/107069028/c41e1500-ccfe-4aa6-b47a-42571f60b335)
> 
> ![Screenshot 2024-05-31 at 14 49 34](https://github.com/openjdk/jfx/assets/107069028/78270097-4ce3-4c3e-8600-aba8d368495c)

This PR presupposes that the scroll bar size and content padding _should_ be changed to be independent of the font size. Since the current choice was a deliberate decision, the issue should be changed to an Enhancement, and we need to consider the possible drawbacks of such a change.

@andy-goryachev-oracle Wait for me to review this.

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PR Comment: https://git.openjdk.org/jfx/pull/1469#issuecomment-2150255521
PR Comment: https://git.openjdk.org/jfx/pull/1469#issuecomment-2150257958