fix: [asset-swapper] MultiHop edge cases

[dekz]

Description

Using includedSources/excludedSources can introduce a few edge cases.

• It modified feeSources which made it difficult to sometimes find an maker/ETH or taker/ETH price, so cost based routing could get weird.
• It can result in MultiHop not having anything to MultiHop to (e.g DAI/USDC with Curve only, theres no ability to ETH hop)
• There are cases where firstHopSource is not present in the FillData but it is required. No valid sources or reverts (didn't dig deep enough to confirm it was a revert)
• If there was no optimal path then we would throw, there's the possibility that there is no optimal path, but there is a MultiHop path available.

Sims on some pairs which use MultiHop often

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.

[moodlezoup]

man this shit is hard, thanks for fixing 😅