RFR: 8254841: Enter or Exit events are shouldn't be displayed while resizing

[Alisen Chung]

Added a resizing flag when the window is currently being resized to block mouseEntered and mouseExited events from being posted to that window.

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Commit messages:
 - moved exceptions into test functions
 - accessing swing components on EDT thread, removed SpuriousExitEnter.java from ProblemList
 - 8254841: Added copyright header
 - 8254841: Enter or Exit events are shouldn't be displayed while resizing

Changes: https://git.openjdk.java.net/jdk/pull/5497/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5497&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254841
  Stats: 211 lines in 4 files changed: 200 ins; 1 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5497.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5497/head:pull/5497

PR: https://git.openjdk.java.net/jdk/pull/5497