chore: translator vs bigfield analysis

[iakovenkos]

Summary

Prototype implementation of BigfieldTranslator as a potential replacement for the Translator VM. Uses bigfield mult_madd with vertical batching to compute the translator accumulation.

Main classes:

• barretenberg/cpp/src/barretenberg/bigfield_translator/bigfield_translator.hpp - New bigfield-based translator circuit
• barretenberg/cpp/src/barretenberg/translator_vm/ - Existing Translator VM (7 relations, 139 subrelations) that this would replace
• barretenberg/cpp/src/barretenberg/flavor/light_zk_flavor.hpp - New minimal ZK flavor with only arithmetic, permutation, delta_range, elliptic, NNF, and ECC op queue relations (no lookups, databus, poseidon2)

Tests:

• barretenberg/cpp/src/barretenberg/bigfield_translator/bigfield_translator.test.cpp - Includes LightZKProveAndVerify test that demonstrates end-to-end proving with the new flavor, and BatchSizeAnalysis test for gate count optimization

Analysis document:

• barretenberg/cpp/src/barretenberg/translator_vm/translator_vm_justification.md