feat: add mav2 signer (#1203)

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This PR introduces a new module for single signer validation in the `account-kit` smart contracts. It adds functionality for packing signatures and validating user operations, along with defining the ABI for the single signer validation module and related contracts.

- Added `PackSignatureParams` type and `packSignature` utility in `utils.ts`.
- Created `SingleSignerValidationModule` with metadata and encoding functions in `single-signer-validation/module.ts`.
- Implemented `singleSignerMessageSigner` function in `single-signer-validation/signer.ts` for signing operations.
- Defined the ABI for `singleSignerValidation` in `abis/singleSignerValidation.ts`.
- Added ABI for `MAV2Factory` and `smaV2` in their respective files.

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