CSSPixels should not be wrapped into CSS::Length before being passed
to resolved() to end up resolving percentages without losing
precision.
Fixes thrashing layout when 33.3333% width is used together with
"box-sizing: border-box".
There were 2 issues with the way we formatted floating point decimals:
if the part after the decimal point exceeded the max of an u64 we would
generate wildly incorrect decimals, and we applied no rounding.
With this new code, we emit decimals one by one and perform a simple
reverse string walk to round the number up if required.
We now produce a `matrix3d()` value when appropriate.
Some sites (such as gsap.com) request the resolved style for `transform`
when there's no viewport paintable, but the element itself does already
have a stacking context. This fixes crashes in that case, because we now
do not access the stacking context at all.
We also do not wrap the result as a StyleValueList any more. The
returned StyleValue is only serialized and exposed to JS, so making it a
StyleValueList has no effect.
