feat: v2 + v3 factory address tracked for better discovery debugging / analysis

[HilliamT]

Motivation

A factory_address field in V2 and V3 proves helpful in understand what pools from which factories are discovered via the PairCreated / PoolCreated event. This can also prove helpful in analysing the contributions from which V2-like / V3-like protocols in pathing e.g 0x-style.

Solution

• Added factory_address to UniswapV2Pool and UniswapV3Pool
• Updated constructors
• Updated tests

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[0xKitsune]

Thanks for the PR, this change makes sense to me!

Thoughts on making the factory_address optional? There are some cases where a user may want to initialize a handful of pools with new_from_address without needing to know the factory.

[HilliamT]

@0xKitsune Apologies for the delay - makes sense for factory_address to be optional.

One later function that can be added as a filter is to filter in only e.g v2 / v3 AMMs with a whitelisted factory_address, especially after discovering other AMMs from merely logs. This does require more thinking of how other AMM cases should be handled though, but can be done later when better thought out.