Return array of FillResults in batch fill methods

[abandeali1]

Description

• Return an array of FillResults for the batch fill variants
• Adds return value tests for all wrapper functions
• Removes formatters from the test-utils package and no longer passes in any null assetData fields into any function calls. Note that we had a task to remove the calldata optimizations in matchOrders and the marketFill functions. For example, in matchOrders we have this rather than checking equality of the assetData fields:

rightOrder.makerAssetData = leftOrder.takerAssetData;
rightOrder.takerAssetData = leftOrder.makerAssetData;

I decided to leave these as is but clarify things a bit more in the comments, since this is actually cheaper than checking equality and still plays nicely with deduped calldata.

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.

[coveralls]

Coverage remained the same at 79.778% when pulling e70b7f3 on feat/3.0/batchFillReturnValues into ba70c11 on 3.0.

[merklejerk]

Nice job!

[hysz]

+1 looks good!