Add funnel metrics

[davidd8]

After discussing w/ @kylehuntsman, some additional metrics to monitor on grafana include measuring the overall autoretrieve funnel (feel free to break out each metric into its own issue as needed):

• Bitswap requests
• Cache Hits (i.e. previously retrieved by Autoretrieve, available to serve immediately)
• Cache Misses (this should result in an Filecoin retrieval request)
• Indexer Requests (should map 1:1 to a cache miss)
• Indexer Response Codes (200, 404, errors)
• Index Misses (either the content is not indexed, or there's an error)
• Filecoin retrieval attempt (should map 1:1 to a 200 indexer response)
• Filecoin retrieval stages (connect, query ask, deal accept, transfer, complete, etc.)
• Filecoin retrieval successes and failures

cc @hannahhoward

[hannahhoward]

@kylehuntsman can you check off which of these are done?

[hannahhoward]

@hannahhoward and @kylehuntsman to pair to try to identify each actual stage.