Support exemplar federated query #10817

Job	Run time
build	4m 2s
lint	4m 16s
test	16m 5s
CodeQL	6m 34s
test-no-race	7m 6s
integration-configs-db	2m 43s
integration (requires_docker)	7m 44s
integration (integration_alertmanager)	3m 59s
integration (integration_backward_compatibility)	10m 21s
integration (integration_memberlist)	7m 16s
integration (integration_querier)	15m 33s
integration (integration_ruler)	5m 33s
integration (integration_query_fuzz)	4m 31s
deploy_website	0s
deploy	0s
	1h 35m 43s

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