Support ABI hashing for static dynamic arrays

[Th0rgal]

Summary

• add a Hashing ECM for keccak256(abi.encode(array)) where the dynamic-array elements have fixed static word width
• cover ABI head/length/payload layout, argument validation, and trust-report assumptions in CompilationModelFeatureTest
• remove a latent duplicate externals field in a feature-test spec that was exposed by rebuilding the file

Verification

• lake build Compiler.Modules.Hashing Compiler.CompilationModelFeatureTest
• lake build PrintAxioms
• python3 scripts/generate_print_axioms.py --check
• python3 scripts/check_axioms.py
• git diff --check

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Note

Medium Risk
Adds a new hashing/codegen module that manipulates calldata and free memory, so incorrect layout/length calculations could silently change contract hashes. Scope is contained and covered by new compilation/Yul layout assertions and validation error tests.

Overview
Adds Compiler.Modules.Hashing.abiEncodeStaticArrayModule (and abiEncodeStaticArray) to compute keccak256(abi.encode(array)) for dynamic-array parameters with static-sized elements, using {param}_length/{param}_data_offset, copying the contiguous payload into free memory, and hashing the ABI head+length+data.

Extends CompilationModelFeatureTest with a smoke spec that asserts key Yul layout properties, plus negative specs for bad ECM arity and zero-width elements; also asserts the trust report includes the new ABI-layout and keccak assumptions. Removes an accidentally duplicated externals block from an unrelated ADT alias payload test spec.

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