Refactor Poseidon sponge types to use const generic arrays instead of vectors

[dannywillems]

Summary

Replace dynamic vector allocations in Poseidon sponge types with fixed-size arrays using const generics, improving memory layout and reducing allocations.

Motivation

The current ArithmeticSpongeParams uses Vec<Vec<F>> for round constants, which:

• Scatters data across the heap
• Requires dynamic allocations during initialization
• Prevents compile-time size verification

Using const generic arrays allows:

• Stack allocation when possible
• Contiguous memory layout
• Compile-time verification of round counts
• Small but consistent performance improvement

[dannywillems]

Previously tracked Investigate if Poseidon subcrate should live in OpenMina or proof-systems #1215.