Improve streaming on MetricsForLabelMatchersStream method #10751

Job	Run time
CodeQL	6m 0s
CodeQL	7m 2s
CodeQL	7m 2s
test	5m 55s
test	36m 43s
test	15m 59s
lint	4m 41s
lint	4m 41s
lint	4m 41s
test-no-race	5m 52s
test-no-race	7m 41s
test-no-race	7m 41s
build	4m 39s
build	4m 15s
build	4m 15s
integration	0s
integration-configs-db	0s
integration-configs-db	2m 42s
integration-configs-db	2m 42s
deploy_website	1s
deploy_website	0s
deploy_website	0s
deploy	1s
deploy	0s
deploy	0s
integration (requires_docker)	8m 1s
integration (requires_docker)	8m 1s
integration (integration_alertmanager)	5m 24s
integration (integration_alertmanager)	5m 24s
integration (integration_backward_compatibility)	10m 42s
integration (integration_backward_compatibility)	10m 42s
integration (integration_memberlist)	7m 44s
integration (integration_memberlist)	7m 44s
integration (integration_querier)	15m 11s
integration (integration_querier)	15m 11s
integration (integration_ruler)	5m 53s
integration (integration_ruler)	5m 53s
integration (integration_query_fuzz)	4m 56s
integration (integration_query_fuzz)	4m 56s
	4h 8m 15s

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