Fix: Replace ccxt.loadMarkets() with the IExchange.loadMarkets() wrapper to cache markets across exchange instances

[bludnic]

This will probably not work. The second exchange will load markets from the exchange and not the database.

import { exchanges, cache } from '@opentrader/exchanges'
import { PrismaCacheProvider } from '@opentrader/exchanges/server'

cache.setCacheProvider(new PrismaCacheProvider())

const exchange1 = exchanges.OKX()
await exchange1.loadMarkets() // from cache

const exchange2 = exchanges.OKX()
await exchange2.fetchTicker('BTC/USDT') // will call `ccxt.loadMarkets()`