<Swing Dev> [jdk16] RFR: 8251377: [macos11] JTabbedPane selected tab text is barely legible

[Prasanta Sadhukhan]

Please review a fix for jdk16.
On macOS 11 (bigsur), using the Swing Aqua Look and Feel, the text of the selected JTabbedPane tab title text is just a light gray outline of white text on a white background. The macOS 11 design inverted from dark background / light text to light background / dark text, so white text on white background is not legible.
Correct system color to use for this scenario, as per Apple, is [NSColor controlTextColor]
so the proposed fix is to use this system color for BigSur. 
For preBigSur releases, "white" is still used as the above color is for text color but the tabPane background color is still not readable through any Apple API, so [NSColor controlTextColor] which returns black will not be legible on preBigSur releases which has black background.

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

Commit messages:
 - 8251377: [macos11] JTabbedPane selected tab text is barely legible

Changes: https://git.openjdk.java.net/jdk16/pull/65/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16&pr=65&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8251377
  Stats: 10 lines in 4 files changed: 8 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/65.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/65/head:pull/65

PR: https://git.openjdk.java.net/jdk16/pull/65