Simplify code gen lib interface #171

Job	Run time
Construct Examples matrix	3s
Benchmarks / Construct Benchmarks matrix	3s
Cxx interop / Construct Cxx interop matrix	3s
Soundness / Check generated code	1m 22s
Soundness / Swift license headers check	7s
Unit tests / Construct unit test matrix	4s
Soundness / API breakage check	1m 11s
Soundness / Broken symlinks check	3s
Soundness / Documentation check	1m 26s
Soundness / Format check	39s
Soundness / License headers check	5s
Soundness / Shell check	34s
Soundness / Python lint check	6s
Soundness / Unacceptable language check	3s
Soundness / YAML lint check	3s
Examples / Linux (6.0)	7m 44s
Benchmarks / Benchmarks / Linux (6.0)	2m 28s
Benchmarks / Benchmarks / Linux (nightly-6.1)	2m 58s
Examples / Linux (nightly-6.1)	3m 5s
Benchmarks / Benchmarks / Linux (nightly-main)	2m 51s
Examples / Linux (nightly-main)	2m 58s
Cxx interop / Cxx interop / Linux (6.0)	59s
Cxx interop / Cxx interop / Linux (nightly-6.1)	1m 6s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 6s
Unit tests / Unit tests / Linux (6.0)	1m 25s
Unit tests / Unit tests / Linux (nightly-6.1)	1m 40s
Unit tests / Unit tests / Linux (nightly-main)	1m 42s
	35m 54s

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