Add tests for generalized and multi-equation morphism

[Chausseaumoine]

This PR adds new unit tests and test utilities for validating generalized Pedersen commitments and DLEQ relations involving multiple equations and generators.

• New test helpers in test_utils.rs:

  • dleq_generalized
  • pedersen_commitment_generalized
  • pedersen_commitment_multi_equation

• New unit tests:

  • Generalized Pedersen commitments with multiple blindings
  • Sets of Pedersen commitments with shared secrets and distinct randomness
  • Generalized DLEQ relations across arbitrary-length basepoints

• Fiat-Shamir verification: both prove_batchable and prove_compact are tested for all new relations.