RFR: 8370140: RichTextArea: line endings [v10]

[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`.
> 
> ### NOTES
> 
> - some dependency on #1938 , resolved.
> - reviewers may use the Monkey Tester with the `CodeArea.lineEnding` property enabled from this branch: https://github.com/andy-goryachev-oracle/MonkeyTest/tree/line.ending

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

  review comments

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1944/files
  - new: https://git.openjdk.org/jfx/pull/1944/files/a27a4410..cfbc542d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1944&range=09
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1944&range=08-09

  Stats: 24 lines in 7 files changed: 4 ins; 0 del; 20 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