Replace num with num-bigint and num-traits

[sile]

Copilot Summary

This pull request includes changes to update dependencies and refactor code to use the new num-bigint and num-traits crates. The most important changes include updating the Cargo.toml file, modifying import statements, and refactoring implementations to use the new crates.

Dependency updates:

• Cargo.toml: Added num-bigint and num-traits dependencies and removed the old num dependency.

Import statement updates:

• src/codec.rs: Updated import statements to use num_bigint instead of num::bigint. [1] [2]
• src/lib.rs: Updated import statements to use num_bigint instead of num::bigint. [1] [2]
• src/pattern.rs: Updated import statements to use num_bigint and num_traits instead of num::bigint and num::traits. [1] [2] [3]

Code refactoring:

• src/convert.rs: Refactored implementations to use num_traits::ToPrimitive and num_bigint::ToBigInt and ToBigUint instead of the old num crate equivalents. [1] [2] [3] [4] [5] [6]

Test file cleanup:

• tests/lib.rs: Removed unnecessary extern crate declarations for eetf and num.