consider switching to zmij for css numeric serialization

[emilio]

https://github.com/dtolnay/zmij, it's supposed to be faster than dtoa-short, but we probably want to check the output.

[nicoburns]

I had a quick look into this, and it looks like it might be viable to me. We are currently using the Notation metadata returned by dtoa-short (here) to fixup the output by adding a .0 in cases where dtoa-short doesn't. But it looks to me like zmij may just output our desired formatting without needing the fixup. For example, dtoa-short formats the Rust float literal 1234.0 as 1234 but zmij formats it as 1234.0.

Is there are test suite or spec for this?

https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=321ae9b56f96ffefc4403cf2369983ba

[emilio]

@nicoburns there are some tests in tree but even better would be to run that change on Firefox / Servo's test-suite. If there are no regressions seems good to go.