Support sandwiches including multiple pools

[lukevs]

Fixes this: #198

For sandwiches, the backrun swap doesn't need to be funded by the sandwicher, it just should end up cycling back to their account

[bertmiller]

if ( other_swap.token_in_address == front_swap.token_in_address and other_swap.token_out_address == front_swap.token_out_address and other_swap.from_address != sandwicher_address ): sandwiched_swaps.append(other_swap)
Does this work if it's a sandwich of a Token -> ETH trade and the sandwich needs to go from ETH-> token -> ETH?

In that case the token in of the first swap would be eth, even though the sandwiched trades would be token.

Separately the issue you're solving here lgtm.

[lukevs]

It'll still work because that ETH => Token => ETH cycle will break into two swaps, and we'll say the "front swap" is the Token => ETH piece

[lukevs]

@bertmiller said lgtm