Support exemplar federated query #10820

Job	Run time
lint	4m 33s
test	15m 44s
build	4m 3s
CodeQL	6m 47s
test-no-race	7m 37s
integration-configs-db	2m 43s
integration (requires_docker)	7m 36s
integration (integration_alertmanager)	4m 2s
integration (integration_backward_compatibility)	10m 16s
integration (integration_memberlist)	7m 44s
integration (integration_querier)	15m 20s
integration (integration_ruler)	5m 50s
integration (integration_query_fuzz)	4m 48s
deploy_website	0s
deploy	0s
	1h 37m 3s

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