fix: Backport Rack proxy event to middleware (#764) #2213

Job	Run time
kafka / racecar / ubuntu-latest	3m 26s
kafka / rdkafka / ubuntu-latest	4m 3s
mysql / mysql2 / ubuntu-latest	54s
kafka / ruby_kafka / ubuntu-latest	1m 22s
other / dalli / ubuntu-latest	1m 17s
mysql / trilogy / ubuntu-latest	48s
other / mongo / ubuntu-latest	1m 14s
postgresql / pg / ubuntu-latest	1m 16s
postgresql / que / ubuntu-latest	1m 0s
rabbitmq / bunny / ubuntu-latest	34s
redis / redis / ubuntu-latest	47s
redis / resque / ubuntu-latest	1m 7s
redis / sidekiq / ubuntu-latest	1m 12s
	19m 0s

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