refact: remove Into<[u64; 4]>, From<[u64; 4]>, and RefInto<[u64; 4]> bounds for trait Scalar

[SuccinctPaul]

It's only a draft.

• blocks by Tidy up scalar module #234
• After this merged, will continue

What changes are included in this PR?

• remove Into<[u64; 4]>, From<[u64; 4]>, and RefInto<[u64; 4]> bounds for trait Scalar

Are these changes tested?

• The PR title and commit messages adhere to guidelines here: https://github.com/spaceandtimelabs/sxt-proof-of-sql/blob/main/CONTRIBUTING.md. In particular ! is used if and only if at least one breaking change has been introduced.
• I have run the ci check script with source scripts/run_ci_checks.sh.

[JayWhite2357]

Quickly glancing over this looks good so far. You mention that it is a draft. I marked it as a Draft PR. Once you feel it is ready, go ahead and mark it as ready for review.