RFR: 8366986: [Win] Incorrect position and size after hiding iconified stage

[Martin Fox]

When a top-level HWND is iconified its window rect is updated to a hard-coded location (something like -32000, -32000) and a smaller width and height. For this reason we should not send notifyMove or notifyResize events for an iconified stage.  This PR adds a check while handling WM_SHOWWINDOW to catch the case where a stage is hidden while iconified. This matches similar existing checks like the one for WM_MOVE.

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Commit messages:
 - Added system test
 - Do not send size or position notifications when iconified

Changes: https://git.openjdk.org/jfx/pull/1889/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1889&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366986
  Stats: 118 lines in 2 files changed: 114 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jfx/pull/1889.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1889/head:pull/1889

PR: https://git.openjdk.org/jfx/pull/1889