/claim #228

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Rationale for this change

What changes are included in this PR?

Replace Into<[u64; 4]>, From<[u64; 4]>, and RefInto<[u64; 4]> trait bounds on Scalar with explicit from_limbs() and to_limbs() methods. This makes the non-free Montgomery form conversions more visible at call sites.

BREAKING CHANGE: Scalar trait no longer requires Into<[u64; 4]>, From<[u64; 4]>, or RefInto<[u64; 4]> bounds. Implementors should use the new from_limbs() and to_limbs() methods instead.

related to changes proposed in #228

Are these changes tested?

Yes