feat(indexer): Use HistoricalFallbackReader for IndexerApi

[tomxey]

This includes:

• query_transaction_blocks:
  • support for case when user filters by checkpoints sequence id
• query_events
  • support for case when user filters by tx digest

Other filters cannot be easily supported right now.

We could consider to support case where we prune the transactions/events table, but don't prune the indices.
In such case we could fetch tx/ev ids from indices, then convert that to digests and fetch txs/evs from KV by digest.
This can be considered in a separate issue.