[feature] simplify service node ping p2p message

[rikublock]

The ServiceNodePing (snp) message currently contains a lot of duplicate information. The entire service node object snode is being serialized and broadcasted.

Current ServiceNodePing structure:

    CPubKey snodePubKey;
    uint32_t bestBlock{0};
    uint256 bestBlockHash;
    uint32_t pingTime{0};
    std::string config;
    ServiceNode snode;
    std::vector<unsigned char> signature;

Additionally, the entire service node config is broadcasted with every ping, even though it rarely changes.

Here three things a proposed:

• Simplify the ping structure, strip away unnecessary/duplicate information.
• Instead of broadcasting the full config with every message, only broadcast the hash of the config. The config to a specific hash can then be requested with a different message.
• Parse the config and only broadcast a well defined native structure as opposed to a mere string, which currently can contain almost anything (comments, large size, platform dependent line endings, etc.)