Persist swap inputs when switching networks

[willhennessy]

Desired Behavior:

1. Enter swap details (e.g. 1 ETH for 120 UNI)
2. Switch networks (e.g. L1 -> Optimism, or Arbitrum, in any direction)
3. The user-entered value should persist. Once the new network is connected, the app should automatically fetch a quote for that trade and display it.

Use case: as a user I want to quickly compare prices across the different networks.

Current Behavior: all user input is dropped when we switch networks