dataspace-protocol: split CN and TP Services

[ndr-brt]

Feature Request

Currently all the "client" and the "protocol" logic stays in the ContractNegotiationService and in the TransferProcessService.
Those could be split in:

• *Service: is meant to contain the logic called internally or by some clients
• *ProtocolService: contains all the logic that need to be executed after receiving a protocol message

Which Areas Would Be Affected?

contract negotiation, transfer process

Why Is the Feature Desired?

cleanup