RFR: 8450: Improve usability of selectable action items by supporting keyboard and double-click interactions

[Aymane Harmaz]

This PR adds more interaction capabilities to tree items and checkbox tables:

- Tree items: Added support for expanding/collapsing via double-click and Enter key press.
- Checkbox table: Added support for enabling/disabling via Enter key press.

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Commit messages:
 - 8450: Improve usability of selectable action items by supporting keyboard and double-click interactions

Changes: https://git.openjdk.org/jmc/pull/682/files
  Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=682&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-8450
  Stats: 136 lines in 6 files changed: 123 ins; 5 del; 8 mod
  Patch: https://git.openjdk.org/jmc/pull/682.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/682/head:pull/682

PR: https://git.openjdk.org/jmc/pull/682