router-sdk: Expand mixed route capabilities

[ewilz]

Trade objects with Mixed Routes can be formed but is still missing some featrures:

• Enable mixed Routes that go from WETH --> ETH intermediary pools. (universal-router-sdk and quoters will need to understand to unwrap WETH from v2/v3 to then trade on a V4 native pool.
• Enable switching between ETH/WETH in potential pure v4 routes. (double check with protocols that PoolManager doesn't inherently already know how to do this)
  • ok solution to this, is ETH-->WETH will actually have to be a hop on a pool that trades ETH/WETH. We can create a custom accounting pool that knows to just wrap/unwrap for this. Create a Custom Accounting hook for ETH/WETH pools that wraps/unwraps v4-periphery#302