fix: NNA quotient length computation edge cases

[ivokub]

Description

This PR fixes edge cases when computing the quotient length. We compute the product length in bits and then to get the quotient length, we subtract the modulus length. But as we work over uints then if the product length is less than the modulus (for example when inputs are short, on one limb), then we get underflow which due to rolling over leads to allocating huge slices. This crashes the prover.

Also fixed a potential edge case in carry computation.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How has this been tested?

Tested with #1339

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[yelhousni]

That makes sense 👍 and I confirm it solves the problem I encountered in #1339.