feat: support initial-response in RPC based event streams #2484

Job	Run time
linux (focal, 5.7)	12m 13s
apple (macos-12, Xcode_14.0.1, platform=iOS Simulator,OS=16.0,name=iPhone 13)	13m 36s
linux (focal, 5.9)	8m 55s
apple (macos-12, Xcode_14.0.1, platform=OS X)	8m 1s
linux (amazonlinux2, 5.7)	12m 15s
apple (macos-13, Xcode_15.0, platform=iOS Simulator,OS=17.0,name=iPhone 14)	22m 36s
linux (amazonlinux2, 5.9)	11m 3s
apple (macos-13, Xcode_15.0, platform=OS X)	11m 35s
	1h 40m 14s

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