RFR: 8267374: (macos) Option+Up/Down arrow dont traverse to beginning/end of line in textarea

[Prasanta Sadhukhan]

Unlike in native "Notes" editor where Option+Up/Down traverses to start/end of each line respectively,
Java does not honour these key combination in editor.

Added the key combination support by moving the caret to start/end of line and then doing caret up/down a line depending on if we are pressing UP or DOWN key.

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Commit messages:
 - Fix
 - Fix

Changes: https://git.openjdk.org/jdk/pull/9230/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9230&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8267374
  Stats: 347 lines in 3 files changed: 347 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9230.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9230/head:pull/9230

PR: https://git.openjdk.org/jdk/pull/9230