[Discussion] add Royalties and Payouts mechanism to Multi Token standard

[uncle-T0ny]

Problem

• We have Royalties and Payouts interface for NFT, but not for Multi Token
• In the Multi Token contract there is no way to receive current token holders, so it's nice to add a view method(through extension) to be able to distribute the royalties

Proposal
Add a Royalties and Payouts standard that is similar to NEP-199 and add a method with the next interface to be able to receive the current token holders with the positive balance.

    /// Get a list of all token holders (with pagination)
    ///
    /// # Arguments:
    /// * `token_id` - ID of the token
    /// * `from_index`: a string representing an unsigned 128-bit integer,
    ///    representing the starting index of accounts to return
    /// * `limit`: the maximum number of accounts to return
    /// returns: List of [AccountId]s.
    ///
    fn mt_token_holders(
        &self,
        token_id: TokenId,
        from_index: Option<U128>,
        limit: Option<u64>,
    ) -> Vec<AccountId>;