pindexer: 💧 add `AppView` for viewing liquidity

[cratelyn]

implement an app view to index liquidity.

LP View

• Position Updates (open/close/withdraw) with their metadata, block number, tx hash, and ideally b64 position id
• Events that cause reserve updates, we do not have all of this data but would ideally like: related tx_hash, block number, final reserve state, the context for the execution (e.g. the trace), along with the type of event that caused the change (e.g. was it an arb vs swap). Basically anything needed to complete this issue https://github.com/penumbra-zone/dex-explorer/issues/24
• block number to timestamp mapping for each event
• The current/live LP status, obtained from the dex service liquidityPositionById method call

- https://github.com/penumbra-zone/dex-explorer/issues/25