added time to interactive metrics
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Added time to interactive metrics and refactored metrics/lib
I need to write tests, but wanted to submit the PR for review
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Wait as late as possible to assign ClipIds
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This will allow Servo to create ClipScrollNodes later during display
list construction, which will be necessary once rounded rectangles
are removed from the LocalClip structure. Instead of keeping track
of the ClipId of each ClipScrollNode, we keep track of its index in an
array of ClipScrollNodes. This will allow us to access them without a
hash lookup.
Update concept of node filter algorithm
Implement new [filter](https://dom.spec.whatwg.org/#concept-node-filter) algorithm from specification
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Add iterpath and iterdir to CSS test runner.
This allows running a subset of the CSS tests again, by specifying
a directory or single test.
Fixes#18931.
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