Migrate CI to use GitHub Actions. #3

Job	Run time
Swift 6 Language Mode	0s
Soundness / API breakage check	2m 13s
Soundness / Broken symlinks check	4s
Soundness / Format check	41s
Soundness / Documentation check	1m 49s
Soundness / License headers check	4s
Soundness / Unacceptable language check	5s
Soundness / YAML lint check	3s
Soundness / Python lint check	6s
Soundness / Shell check	38s
Cxx interop / Cxx interop / Linux (5.9)	1m 26s
Cxx interop / Cxx interop / Windows (6.0)	1s
Cxx interop / Cxx interop / Linux (5.10)	1m 21s
Cxx interop / Cxx interop / Windows (nightly-6.0)	1s
Cxx interop / Cxx interop / Linux (6.0)	1m 35s
Cxx interop / Cxx interop / Windows (nightly-main)	2s
Cxx interop / Cxx interop / Linux (nightly-6.0)	1m 50s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 54s
Unit tests / Unit tests / Linux (5.9)	2m 48s
Unit tests / Unit tests / Windows (6.0)	3s
Unit tests / Unit tests / Linux (5.10)	2m 47s
Unit tests / Unit tests / Linux (6.0)	1m 25s
Unit tests / Unit tests / Linux (nightly-6.0)	3m 11s
Unit tests / Unit tests / Windows (nightly-6.0)	1s
Unit tests / Unit tests / Linux (nightly-main)	3m 11s
Unit tests / Unit tests / Windows (nightly-main)	3s
	27m 22s

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