RFR: 8368185: Test javax/swing/plaf/synth/SynthButtonUI/6276188/bug6276188.java failed: Synth ButtonUI does not handle PRESSED & MOUSE_OVER state

[Prasanta Sadhukhan]

Test frame is changed to Red for Mouse PRESSED and MOUSE_OVER state but it seem time is too less before it is moved to Green when mouse press is released so it retrieves Green instead of Red.
Also, the pixel color retrieval point is conflicting with mouse cursor position, which gets picked up during `robot.createSceenCapture` execution so retrieval point is moved slightly up instead of down.

100 iterations of the test passed in all platforms.

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Commit messages:
 - 8368185: Test javax/swing/plaf/synth/SynthButtonUI/6276188/bug6276188.java failed: Synth ButtonUI does not handle PRESSED & MOUSE_OVER state

Changes: https://git.openjdk.org/jdk/pull/27444/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27444&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368185
  Stats: 27 lines in 1 file changed: 16 ins; 5 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/27444.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27444/head:pull/27444

PR: https://git.openjdk.org/jdk/pull/27444