Check no_std compatibility in CI and fix remaining use of std

[Jondolf]

Objective

It can be easy to accidentally break no_std compatibility. We should check it in CI!

We're also missing some f32 method lints in clippy.toml, and are still actually using std::f32::round in one place.

Solution

Add no_std checks to CI, and add the remaining f32 method lints to clippy.toml. Through this I also discovered that we need a critical-section feature for Bevy in some no_std environments.

The check is based on no_std library example.