[WIP] Integer multiplication implementation

[shinta-liem]

Basic grade-school algorithm for integer multiplication for x and y where x is a positive unsigned number, and y is a signed number in two's complement.

This is a WIP:

• Use the correct step and context
• Optimize the algorithm -- calculate the interim products and add it up in parallel
• Explore more efficient algorithm

[benjaminsavage]

@danielmasny - thanks for sharing that write-up! I think we should definitely try both approaches (and I have a few more in mind as well). The tradeoff here is communication cost vs the simplicity of remaining in a boolean field.

I do not expect the schoolbook multiplication algorithm to be the most efficient. I mainly view this as a simple onboarding task for @shinta-liem - to help familiarise her with the Rust codebase. We can implement this alternative approach as well in a follow-up PR and benchmark them against one another.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 99.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.05%. Comparing base (671fb4d) to head (701803e).

Files	Patch %	Lines
ipa-core/src/protocol/ipa_prf/boolean_ops/step.rs	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1174 +/- ## ========================================== + Coverage 92.01% 92.05% +0.03% ========================================== Files 195 196 +1 Lines 29130 29241 +111 ========================================== + Hits 26805 26917 +112 + Misses 2325 2324 -1 ```

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