Codegen revamp #803

Job	Run time
Check Examples	1m 16s
clippy (async-std-surf)	1m 43s
format	13s
clippy (tokio-hyper)	1m 25s
Docs	53s
clippy (tokio-hyper-rustls)	1m 18s
clippy (tokio-hyper-rustls-webpki)	1m 16s
test (async-std-surf)	4m 19s
verify-codegen-crate	37s
clippy (blocking)	1m 25s
test (tokio-hyper)	5m 8s
clippy (blocking-rustls)	1m 16s
clippy (blocking-rustls-webpki)	1m 18s
test (tokio-hyper-rustls)	5m 16s
test (tokio-hyper-rustls-webpki)	5m 20s
test (blocking)	5m 25s
test (blocking-rustls)	5m 16s
test (blocking-rustls-webpki)	5m 29s
	48m 53s

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