Add a dev-tool subpackage #221

Job	Run time
Construct Examples matrix	2s
Benchmarks / Construct Benchmarks matrix	3s
Cxx interop / Construct Cxx interop matrix	5s
Soundness / Check generated code	1m 13s
Soundness / Swift license headers check	7s
Unit tests / Construct unit test matrix	3s
Soundness / Broken symlinks check	3s
Soundness / API breakage check	1m 18s
Soundness / Documentation check	1m 25s
Soundness / Format check	36s
Soundness / License headers check	8s
Soundness / Python lint check	6s
Soundness / Shell check	43s
Soundness / Unacceptable language check	5s
Soundness / YAML lint check	3s
Examples / Linux (6.0)	14m 8s
Examples / Linux (nightly-6.1)	3m 41s
Examples / Linux (nightly-main)	3m 36s
Benchmarks / Benchmarks / Linux (6.0)	2m 34s
Benchmarks / Benchmarks / Linux (nightly-6.1)	3m 1s
Benchmarks / Benchmarks / Linux (nightly-main)	2m 52s
Unit tests / Unit tests / Linux (6.0)	1m 31s
Unit tests / Unit tests / Linux (nightly-6.1)	1m 54s
Unit tests / Unit tests / Linux (nightly-main)	1m 42s
Cxx interop / Cxx interop / Linux (6.0)	1m 4s
Cxx interop / Cxx interop / Linux (nightly-6.1)	1m 3s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 0s
	44m 6s

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