RFR: 8348736: RichTextArea clamp and getText [v2]

[Andy Goryachev]

> Fixes minor issues uncovered while writing API tests #1677:
> 
> - StyledTextModel::clamp L559 is incorrect at the end of paragraph
> - CodeArea.getText() adds extra newline at the end
> 
> This change should be back-ported to jfx24.

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/1684/files
  - new: https://git.openjdk.org/jfx/pull/1684/files/a55dc8db..ff8942b8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1684&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1684&range=00-01

  Stats: 8 lines in 2 files changed: 5 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1684.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1684/head:pull/1684

PR: https://git.openjdk.org/jfx/pull/1684