Add multiticker datasources

To reduce API requests, we can fetch prices for multiple tickets using a single request. This is necessary since most of the public APIs have strict usage limits.

https://api.coingecko.com/api/v3/simple/price?ids=razor-network%2Cethereum&vs_currencies=usd

Razor-go should cache it for short-term use (4 mins, e.g.) the results instead of querying it again and again.