feat(statement-distribution): Implement `answer_request`

### Description

The function [`answer_request `](https://github.com/paritytech/polkadot-sdk/blob/41a5d8ec5f3d3d0ff82899be66113b223395ade5/polkadot/node/network/statement-distribution/src/v2/mod.rs#L3245-L3246) should handle [`AttestedCandidateRequest`](https://github.com/paritytech/polkadot-sdk/blob/82117ad53fc68e8097183e759926b62265ffff0a/polkadot/node/network/protocol/src/request_response/v2.rs#L32) and respond the peer who send it, also should check if the peer is allowed to request the candidate (i.e. they're in the cluster or we've sent them a manifest), should responde with [`AttestedCandidateResponse`](https://github.com/paritytech/polkadot-sdk/blob/82117ad53fc68e8097183e759926b62265ffff0a/polkadot/node/network/protocol/src/request_response/v2.rs#L47)