RFR: 8261221: Tooltip bigger than screen size blinks - shows and hides over and over again

[Paweł Kruszczyński]

`Tooltip` is no longer hiding upon receiving `MouseEvent.MOUSE_ENTERED_TARGET` event inside it. Pressing mouse on overlaying tooltip also kills the tooltip, so the infinite duration tooltip can be closed.

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Commit messages:
 - 8261221: Tooltip bigger than screen size blinks - shows and hides over and over again

Changes: https://git.openjdk.java.net/jfx/pull/395/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=395&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261221
  Stats: 24 lines in 1 file changed: 24 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/395.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/395/head:pull/395

PR: https://git.openjdk.java.net/jfx/pull/395