Improve RelationshipModule storing and discoverability.

[Ramarti]

Current relationship storing works like this:

mapping(uint256 => LibRelationship.Relationship) private _relationships;
mapping(bytes32 => uint256) private _relHashes;

// Store
LibRelationship.Relationship memory rel = LibRelationship.Relationship({
            relType: createParams.relType,
            srcAddress: createParams.srcAddress,
            dstAddress: createParams.dstAddress,
            srcId: createParams.srcId,
            dstId: createParams.dstId
        });
_relationships[relationshipId] = rel;
_relHashes[keccak256(abi.encode(rel))] = relationshipId;


// Discovering
function getRelationshipId(LibRelationship.Relationship calldata rel_) external virtual override view returns (uint256) {
        return _relHashes[keccak256(abi.encode(rel_))];
}

This only works if you already know of the 2 ends of the relationship, but we need a way to tell if 1 node is part of a relationship, and also traverse the actual graph, also up the relationship directions, for invalidations.