RFR: 8302173: Button border overlaps with button icon on macOS system LaF

[Damon Nguyen]

Previous fix to HTML in AquaButtonUI fixed spacing issue for HTML images in a JButton in Aqua L&F. The new issue comes from having text inside the HTML as the button's text. If an icon is used, this icon exceeds the bounds of the button and overlaps the border.

Added additional logic to check if HTML contains an img. If so, apply the previous fix. Otherwise, the original implementation for Aqua's JButton HTML layout works correctly, so use this behavior.

Added a test based on the provided test in the bug report. Automated the test using a BufferedImage and changed the icon color to RED. Tested with multiple runs on Aqua L&F, and the test passes with the update where it fails without the update.

-------------

Commit messages:
 - Fix whitespace error
 - Add ending line in test
 - Update AquaButton conditional. Add automated test for Aqua

Changes: https://git.openjdk.org/jdk/pull/12520/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12520&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302173
  Stats: 174 lines in 2 files changed: 162 ins; 3 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/12520.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12520/head:pull/12520

PR: https://git.openjdk.org/jdk/pull/12520