Add libm feature to allow no_std compilation

[bushrat011899]

Objective

Currently, no_std targets such as wasm32v1-none fail to compile, as num-traits has its std feature permanently enabled. Additionally, without std linked, several important floating point methods are unavailable. This can be fixed by using num-traits::Float and enabling the libm feature.

Solution

• Disable default features on num-traits to ensure std is not unconditionally enabled.
• Add a new libm feature which enables num-traits/libm
• Add num-traits/std to the std feature
• Enable std by default

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Notes

• No AI tooling of any kind was used during the creation of this PR.