Add users stats http api to ingester #222

Job	Run time
build	3m 59s
CodeQL	6m 19s
lint	2m 29s
test	21m 37s
integration-configs-db	2m 28s
integration (requires_docker)	6m 17s
integration (integration_alertmanager)	4m 18s
integration (integration_backward_compatibility)	8m 44s
integration (integration_memberlist)	8m 2s
integration (integration_querier)	12m 8s
integration (integration_ruler)	4m 18s
integration (integration_query_fuzz)	2m 31s
deploy_website	0s
deploy	0s
	1h 23m 10s

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