RFR: 8374909: CodeArea: Exception in IME [v2]

[Andy Goryachev]

> Fixes a bug which was reported in https://github.com/andy-goryachev-oracle/Test/issues/6#issuecomment-3726867016 (introduced by adding IME support https://bugs.openjdk.org/browse/JDK-8368478 )
> 
> Adds proper clamping and normalization of selection range within the `StyledTextModel`, and replaces the implementation of getText() with the standard export().

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

  limit

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Changes:
  - all: https://git.openjdk.org/jfx/pull/2029/files
  - new: https://git.openjdk.org/jfx/pull/2029/files/46ef7baa..f7405a19

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=2029&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=2029&range=00-01

  Stats: 84 lines in 2 files changed: 81 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/2029.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/2029/head:pull/2029

PR: https://git.openjdk.org/jfx/pull/2029