[NeoSwaps] Remove duplicate `outcomes`, move `outcomes` to `Market`

[maltekliemann]

It's a bad sign that it's impossible for us to retreive the assets that are traded in a particular market, given the market_id. List of possible solutions:

• Add assets vector to Market, allowing us to remove outcomes completely
• Add market_id to Market and use it to implement outcomes
• Make outcomes a function of the market ID. (Seems odd)