fix(css_formatter): improve CSS numeric formatting

[ah-yu]

Summary

Improve CSS numeric formatting with two changes:

• For cases like .5em, ensure the numeric part is formatted as a number rather than simply printing the token as-is.
• Remove trailing zeros in cases like x.0000.
  Prettier formats such numbers differently across languages. In JavaScript, x.0000 is formatted as x.0, whereas in CSS, it is formatted as x.

Closes #5031
Closes #5005

Test Plan

Added tests

[codspeed-hq]

CodSpeed Performance Report

Merging #5052 will not alter performance

_{Comparing ah-yu:fix/num-fmt (9dc87f3) with next (de27f6f)}

Summary

✅ 94 untouched benchmarks

[dyc3]

This would also effectively close #5005, right? Since this makes the formatter conflict with that rule.

[ematipico]

I'm in favour with closing the rule, there's no need for that now

[ematipico]

Thank you!

[ah-yu]

This would also effectively close #5005, right? Since this makes the formatter conflict with that rule.

Yes, I think the formatter has already handled the trailing zeros for us.