Auto merge of #17150 - asajeffrey:script-paint-worklets-plumbing, r=jdm

Implemented the plumbing for paint worklets

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This PR implements the plumbing for paint worklets:

* Adding CSS values for paint worklets.
* Implementing a skeleton for the `PaintWorkletGlobalScope` webidl.
* Implementing an executor for paint worklet tasks, and passing it from script to layout.
* Building the display list items for paint worklet images.

This PR does not implement registering or calling paint worklets in JS.

Before it merges, this PR needs a reftest added for basic paint worklet functionality.

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- [ ] There are tests for these changes

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