* refactor grafana_index_server_index_size to calculate in a goroutine instead of at scrape time and remove grafana_index_server_indexed_docs metric
* use wire to inject bleve index metrics
* remove sprinkles metrics from bleve index metrics
* log error when trying to calculate file index size and bump interval to 1m instead of 5s
* Adds back indexer metrics. Uses config values instead of hardcoded ones.
* cast to int64
* remove unused func
* Index metrics impl doesn't depend on Bleve. Adds a TotalDocs func to SearchBackend interface.
* adds config setting for index_min_count
* rename arg
* rename metric label to namespace instead of slug
* adds default "do nothing" case to satisfy linter
* moves bleve index metrics to search package
* make bleve backend private, dont need to pass in prom reg
* imports
* adds bleve metrics to resource package to avoid circular deps
