pindexer: 🧂 add an `AppView` for block contents

[cratelyn]

implement an app view indexing some basic metadata:

Block View (just 1 block's info)

• All LPs updates for a block, ideally with their b64 id. Aside from metadata need the state change (opened/closed/withdrawn)
• Batch Swaps -- currently looking to use SwapExecutions on dex query service however it returns no data https://github.com/penumbra-zone/penumbra/issues/4618
• Arbs - currently using the dex query service ArbExecutions endpt to get arbs and their traces
• Block number to timestamp mapping

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