RFR: 8341670: [Text, TextFlow] Public API for Text Layout Info [v4]

[Andy Goryachev]

> The RichTextArea control ([JDK-8301121](https://bugs.openjdk.org/browse/JDK-8301121)), or any custom control that needs non-trivial navigation within complex or wrapped text needs a public API to get information about text layout.
> 
> This change fixes the missing functionality by adding a new public method to the `Text` and `TextFlow` classes.:
> 
> 
>     /**
>      * Obtains the snapshot of the current text layout information.
>      * @return the layout information
>      * @since 24
>      */
>     public final LayoutInfo getLayoutInfo()
> 
> 
> The immutable `LayoutInfo` structure contains information about:
> 
> - text lines: offsets and bounds
> - overall layout bounds
> 
> TBD:
> 
> the platform can also report additional information such as:
> 
> - individual text lines' left and right side bearings (what are those?)
> - text runs within each line

Andy Goryachev has updated the pull request incrementally with one additional commit since the last revision:

  clarify

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1596/files
  - new: https://git.openjdk.org/jfx/pull/1596/files/04c4abb1..6869c76f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1596&range=03
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1596&range=02-03

  Stats: 9 lines in 3 files changed: 4 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/1596.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1596/head:pull/1596

PR: https://git.openjdk.org/jfx/pull/1596