Add a macro to instantiate bivariate_sumcheck tests

[GraDKh]

TL;DR

Moved bivariate sumcheck tests from individual modules to a centralized location using a macro.

What changed?

• Removed test modules from bivariate_mlecheck.rs and bivariate_product.rs
• Added a new macro instantiate_bivariate_sumcheck_tests! in bivariate_sumcheck.rs that generates the test functions
• Created a new test file bivariate_sumcheck.rs that uses the macro to instantiate tests for both CPU and Fast CPU layers

How to test?

Run the tests to ensure they still pass:

cargo test --package binius-core --test bivariate_sumcheck

Why make this change?

This refactoring improves code organization by:

1. Centralizing test logic in a single location
2. Reducing code duplication through the use of a macro
3. Making it easier to maintain and extend tests for different compute layer implementations

[GraDKh]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Extract macro to instantiate ring switch tests #785
• Add a macro to instantiate bivariate_sumcheck tests #783 👈 (View in Graphite)
• Introduce macros to instantiate compute layer test #782
• Add core_test_utils crate and move core tests there #781
• Move compute test utils to a different folder #780
• main

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[djadjka]

LGTM