asset-swapper: DFB support + refactors

[dorothy-zbornak]

Description

This adds DexForwarderBridge support AS. When creating the orders, we batch contiguous bridge paths into a single DFB order, so it only pays a single protocol fee. This functionality can be disabled with the shouldBatchBridgeOrders SwapQuoter option.

I've also massively refactored swap_quote_calculator.ts. I created some new functions in quote_simulation.ts whose responsibility is to simulate filling the quote. These first transform the quote orders into a side-agnostic format to remove the need for all the nasty branching logic. So instead of filling a straight maker -> taker asset order, it ends up filling input -> output orders.

We also now have best-case gas estimation and best-case source composition (i.e., what sources were actually used). So now bestCaseQuoteInfo.gas <= worstCaseQuoteInfo.gas, where they were previously equivalent. Also sourceBreakdown now only includes the sources consumed in the best case, so no fallback orders.

Testing instructions

Types of changes

Checklist:

• Prefix PR title with [WIP] if necessary.
• Add tests to cover changes as needed.
• Update documentation as needed.
• Add new entries to the relevant CHANGELOG.jsons.

[dorothy-zbornak]

So now orders have an array of collapsed fills instead of a single one. Fun.

[dorothy-zbornak]

A consequence of this new approach is that both the maker (in buys) and taker (in sells) asset amounts can theoretically deviate from the input amount slightly when fees are involved. In practice they're probably almost always the same though. So if we want to reference a fixed buy or sell amount in the API, we should be using the quote.makerAssetAmount or quote.takerAssetFillAmount, not the best or worst case values. Just something to note.

[coveralls]

Coverage decreased (-0.1%) to 79.462% when pulling c541340 on feat/asset-swapper/DexForwarderBridge-support into d9be78c on development.