Add distributor per labelset received samples metric #10777

Job	Run time
test	16m 7s
build	4m 4s
lint	4m 20s
CodeQL	7m 3s
test-no-race	7m 22s
integration (requires_docker)	7m 16s
integration-configs-db	2m 52s
integration (integration_alertmanager)	4m 20s
integration (integration_backward_compatibility)	10m 21s
integration (integration_memberlist)	8m 2s
integration (integration_querier)	15m 41s
integration (integration_ruler)	5m 33s
integration (integration_query_fuzz)	4m 47s
deploy_website	0s
deploy	0s
	1h 37m 48s

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