RFR: JDK-8296387: [Tooltip, CSS] -fx-show-delay is only applied to the first tooltip that is shown before it is displayed [v2]

[Marius Hanl]

> This PR fixes a long standing issue where the `Tooltip` will always wait one second until it appears the very first time, even if the 
> `-fx-show-delay` was set to another value.
> 
> The culprit is, that the `cssForced` flag is not inside `Tooltip`, but inside the `TooltipBehaviour`. So the very first `Tooltip` gets processed correctly, but after no `Tooltip` will be processed by CSS before showing, resulting in the set `-fx-show-delay` to not be applied immediately.
> 
> Added a bunch of headful tests for the behaviour since there were none before.

Marius Hanl has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  JDK-8296387: [Tooltip, CSS] -fx-show-delay is only applied to the first tooltip that is shown before it is displayed

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1394/files
  - new: https://git.openjdk.org/jfx/pull/1394/files/6d40b527..a4a1a49f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1394&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1394&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1394.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1394/head:pull/1394

PR: https://git.openjdk.org/jfx/pull/1394