Adapt the balancer-sdk SOR to not use coingecko requests

[lgahdl]

The frontend team cannot use Coingecko API Key without exposing it, so we need to find another way to fetch token prices for the SOR functionality.

Franz suggested to use the API:
the API does not offer a “getPriceForToken” option but rather gives you all token prices for a specific (or multiple) chains. I assume you only need current and not historical prices?
the return value for “getCurrentTokenPrices” are price and contract address
{
tokenGetCurrentPrices(chains: [MAINNET]) {
address
price
}
}