Enable basic SVG-related CSS properties for Servo

[mu-mostafa98]

Removes engine = "gecko" from 11 SVG-specific CSS properties to be enabled for servo:

• Fill (3): fill, fill-opacity, fill-rule
• Stroke (8): stroke, stroke-width, stroke-linecap, stroke-linejoin, stroke-dasharray, stroke-dashoffset, stroke-miterlimit, stroke-opacity

Also updates the ComputedValues size test (224 → 232) for the new fields.

Servo PR

[xiaochengh]

Thanks for working on this!

We discussed offline and found this all-in-one PR hard to review. We will change the plan:

• First, enable only a small set of properties for basic shapes in Stylo
• And then, implement the basic shapes and these properties in Servo
• Iterate the above process, and progressively enable more properties in Stylo and implement them in Servo

This way we can make sure that we don't introduce any unintended changes.

[xiaochengh]

Looks good in its current shape now. Let's move focus to the Servo PR.

[nicoburns]

Why have the "geometric attributes" (x, y, cx, cy, rx, ry) been reverted? I think those will be needed for even a minimal implementation of SVG.

[mu-mostafa98]

Why have the "geometric attributes" (x, y, cx, cy, rx, ry) been reverted? I think those will be needed for even a minimal implementation of SVG.

I reverted them just to keep this PR strictly focused on fill and stroke so we can get them tested with WPT in Servo. Don't worry, geometric attributes are coming in the very next PR! That will go hand-in-hand with the Servo PR implementing the DOM elements for shapes (rect, circle, ellipse) that actually use them.