RFR: 8358255: Factor out boilerplate code of EventHandler properties in Scene and Window

[John Hendrikx]

On Sun, 1 Jun 2025 21:42:17 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

> `EventHandler` property implementations in `Scene` and `Window` use anonymous classes derived from `ObjectPropertyBase`. We can remove about 650 lines of boilerplate code by using a common property class instead.

I think this is a huge improvement, and a net win overall.

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Marked as reviewed by jhendrikx (Reviewer).

PR Review: https://git.openjdk.org/jfx/pull/1819#pullrequestreview-2893341470