Codegen revamp #795

Job	Run time
Docs	1m 3s
format	14s
clippy (async-std-surf)	1m 43s
test (async-std-surf)	4m 15s
clippy (tokio-hyper)	1m 29s
verify-codegen-crate	1m 40s
test (tokio-hyper)	4m 33s
clippy (tokio-hyper-rustls)	1m 28s
test (tokio-hyper-rustls)	4m 33s
clippy (tokio-hyper-rustls-webpki)	1m 25s
test (tokio-hyper-rustls-webpki)	4m 37s
clippy (blocking)	1m 27s
test (blocking)	4m 35s
clippy (blocking-rustls)	1m 25s
test (blocking-rustls)	4m 36s
clippy (blocking-rustls-webpki)	1m 24s
test (blocking-rustls-webpki)	4m 35s
	45m 2s

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