Update colorpicker.ts onValueChanged enabled second parameter, event/state

[HiGregSmith]

Added target and currentTarget properties to ColorPicker onValueChangedObservable.

Test with this playground: https://playground.babylonjs.com/?snapshot=refs/pull/17322/merge#ZMLBW6#8

See this forum post for more details: https://forum.babylonjs.com/t/obtain-gui-component-within-onvaluechangedobservable-on-slider-and-colorpicker/61045/8

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

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Interaction tests

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Interaction tests

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Devhost visualization test reporter:

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Visualization tests for WebGPU

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[georginahalpern]

I updated the description to link to the forum post / test playground. Thanks!