Update DEX endpoints

[martinkersner]

Updates

This PR merges Candle and Trade structs under new name Dex. chains, exchanges, pools and intervals functions for DEX-related structs have been moved under Dex as well.

How to use?

let dex: datamaxi::dex::Dex = datamaxi::api::Datamaxi::new(api_key);

// Chains
dex.chains();

// Exchanges
dex.exchanges();

// Pools
let pools_options = datamaxi::dex::PoolsOptions::new();
dex.pools(pools_options);

// Intervals
dex.intervals()

// DEX Trade example
let trade_options = datamaxi::dex::TradeOptions::new().limit(5);
dex.trade(
    "bsc_mainnet",
    "pancakeswap",
    "0xb24cd29e32FaCDDf9e73831d5cD1FFcd1e535423",
    trade_options,
);

// DEX Candle example
let params = datamaxi::dex::CandleOptions::new();
dex.candle(
    "bsc_mainnet",
    "pancakeswap",
    "0xb24cd29e32FaCDDf9e73831d5cD1FFcd1e535423",
    params,
);

[hayotbisonai]

LGTM!