RFR: 8348423: [TestBug] stress test Nodes initialization from a background thread [v2]

[Andy Goryachev]

On Fri, 31 Jan 2025 23:02:35 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> I think this change is why the Tooltip test is no longer failing. The failure mode reported in [JDK-8348100](https://bugs.openjdk.org/browse/JDK-8348100) happens when  constructing Tooltip on a background thread.
>
> The very first (visible) node should be created in the FX application thread (something I missed earlier).  All other instances are created in the background thread - notice the second call to `generator.get()` inside the background thread lambda.

> Related to this, I think a separate set of tests where we construct instances of the node in a loop would be useful, in addition to the set of tests that mutates the node in a loop.

this is a good idea!  thank you.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1690#discussion_r1938073217