performance(starknet-classes): Simplify decompression by using bit alignment of encoding.

[orizi]

Summary

Optimized the decompress function in felt252_vec_compression.rs by replacing the manual limb-by-limb division with a more efficient bit manipulation approach. The new implementation uses a bit mask and shifting operations to extract values from the packed data, which is more performant than the previous division-based algorithm. Also extended the IntoOrPanic trait to support i128 and u128 types.

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Type of change

Please check one:

• Bug fix (fixes incorrect behavior)
• New feature
• Performance improvement
• Documentation change with concrete technical impact
• Style, wording, formatting, or typo-only change

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Why is this change needed?

The previous implementation of the decompress function used a relatively expensive division operation for each word extraction. By leveraging the fact that the padded code size is a power of 2, we can use more efficient bit manipulation operations (masking and shifting) to achieve the same result with better performance.

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What was the behavior or documentation before?

The previous implementation used a manual 4-limb long division approach to extract values from packed data, which was less efficient, especially for large inputs.

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What is the behavior or documentation after?

The new implementation uses bit manipulation (masking and shifting) to extract values from the packed data, which is more efficient. It also adds i128 and u128 implementations for the IntoOrPanic trait to support the new code.

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Additional context

This optimization maintains the same functionality while improving performance. The approach takes advantage of the fact that the padded code size is a power of 2, allowing us to use bit operations instead of division.

[reviewable-StarkWare]

This change is 

[orizi]

• performance(starknet-classes): Simplify decompression by using bit alignment of encoding. #9607 👈 (View in Graphite)
• main

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