feat: Compiled Gates for GKR

[Tabaie]

"Compile" GKR gates into a simple bytecode to reduce frontend.Variable conversions in the backend.

Compared to the baseline #1616 on a MiMC hash of length 65536:
2.9% faster (3.64s vs 3.75s)
5.0% less memory (1.73 GB vs 1.82 GB)
84.2% fewer allocations (696K vs 4.42M - 6.3x reduction)

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Note

Introduces compiled gates and evaluator-based execution to reduce conversions and allocations across GKR.

• Compile gate functions once (gkrtypes.CompileGateFunction) and store in registry; replace gateVerifier with curve-specific GateTester using compiled gates
• Add stack-based gateEvaluator and gateEvaluatorPool for executing compiled gate bytecode; remove frontend.Variable-based gate evaluation paths
• Update prover/verification paths (computeGJ, next, Complete, solver hints) to push inputs and evaluate via gateEvaluator, with memory pooling via polynomial.Pool
• Adjust tests/templates to new GateTester API (IsAdditive, FindDegree, VerifyDegree, Equal) and compiled gates
• Minor API changes: gkrtypes.NewGate now accepts compiled gate; registry enforces equality/degree via GateTester

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