Prepare 1.16.0-rc release #7986

Job	Run time
test	30m 39s
build	3m 59s
lint	29m 53s
integration-configs-db	3m 18s
integration (requires_docker)	7m 47s
integration (integration_alertmanager)	3m 59s
integration (integration_backward_compatibility)	10m 33s
integration (integration_memberlist)	9m 29s
integration (integration_querier)	14m 14s
integration (integration_ruler)	3m 37s
integration (integration_query_fuzz)	3m 1s
deploy_website	0s
deploy	0s
	2h 0m 29s

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