feat: swaps indexing

[vacekj]

Describe your changes

implements indexing of swaps to satisfy the /api/swaps endpoint

• There's also an event for Swap, so we should name the event in the code to BatchSwap to avoid confusion.
• We probably want to record some more information in the swap table, like having the trading pair there, the total amount of inputs and outputs for each asset, the unfilled amounts, et.c

Issue ticket number and link

fixes #4744

Checklist before requesting a review

• If this code contains consensus-breaking changes, I have added the "consensus-breaking" label. Otherwise, I declare my belief that there are not consensus-breaking changes, for the following reason:

  Indexer-only changes

[cronokirby]

We probably want to record some more information in the swap table, like having the trading pair their, the total amount of inputs and outputs for each asset, the unfilled amounts, et.c

[cronokirby]

There's also an event for Swap, so we should name the event in the code to BatchSwap to avoid confusion.

[zmanian]

I believe this PR would unlock using the native indexer to get things like 24 hour swap volumes which would be really helpful to go to market efforts.

How can I support getting it merged?