Should handle decryption requests validity check in new FHE lib

Should probably handle the validation check in the callback selector directly.
 
- https://github.com/zama-ai/fhevm-contracts/blob/8b63bae197bed319fe11ea45fd7438716c7cdf55/contracts/governance/ConfidentialGovernorAlpha.sol#L445
- https://github.com/zama-ai/fhevm-contracts/blob/8b63bae197bed319fe11ea45fd7438716c7cdf55/contracts/governance/ConfidentialGovernorAlpha.sol#L501