Bundle of arguments for setting up an indexer cluster (an Indexer and its associated Metrics
service). This struct is offered as a convenience for the common case of parsing command-line
arguments for a binary running a standalone indexer and its metrics service.
An opinionated IndexerCluster that spins up an Indexer implementation using Postgres as its
store, along with a MetricsService and a tracing subscriber (outputting to stderr) to provide
observability. It is a useful starting point for an indexer binary.