RFR: 8370140: RichTextArea: line endings [v4]

[Andy Goryachev]

> Adds control of line endings (newline separators) in `StyledTextModel`, `RichTextArea`, and `CodeArea`.
> 
> The impacted areas are:
> - saving to plain text
> - copying to plain text
> - IME
> 
> This feature is implemented as a regular field in the `StyledTextModel` (since it is ultimately an attribute of the model), and as a property in the `CodeArea`.
> 
> NOTE:
> - this PR and #1938 are interrelated; it's probably better for #1938 to go first.

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

  since

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1944/files
  - new: https://git.openjdk.org/jfx/pull/1944/files/2d7dbbb9..7c3b1079

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1944&range=03
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1944&range=02-03

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1944.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1944/head:pull/1944

PR: https://git.openjdk.org/jfx/pull/1944