script: Expose id to LargestContentfulPaint - #46828

I'm not sure happy with the way the element id is stored in the fragment tree, but this whole thing also depends on script having access to the Element itself as well. If that happens successfully we don't actually need to roundtrip the element id string into the fragment tree. Still, I'm not sure I understand how we can get the Element safely.

Id is resolved now using Element.