u256: log, log2 and sqrt impl (#5329)

[sudhackar]

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Description

simple changes that uses newton's method for sqrt and decomposition to u64 for log2 - log builds up on log2 for u256

This should fix #5329

Ping @SwayStar123

Checklist

• [x] I have linked to any relevant issues.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [ ] I have updated the documentation where relevant (API docs, the reference, and the Sway book).
• [x] I have added tests that prove my fix is effective or that my feature works.
• [ ] I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• [x] I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• [x] I have requested a review from the relevant team or maintainers.

[sudhackar]

Sorry for closing the old PR - it closed when I rolled back the 2 commits automatically.