ci: Finish migration to Github Actions #75

Job	Run time
Compatibility test	4m 54s
Swift 6 Language Mode	0s
Soundness / API breakage check	2m 47s
Example packages / Linux (5.8)	23s
Example packages / Linux (5.9)	16m 3s
Example packages / Linux (5.10)	14m 46s
Soundness / Documentation check	1m 40s
Example packages / Linux (nightly-6.0)	22m 2s
Example packages / Linux (nightly-main)	30s
Soundness / Unacceptable language check	3s
Integration test / Linux (5.8)	23s
Soundness / Broken symlinks check	3s
Integration test / Linux (5.9)	1m 39s
Integration test / Linux (5.10)	1m 26s
Integration test / Linux (nightly-6.0)	2m 7s
Soundness / Format check	37s
Integration test / Linux (nightly-main)	37s
Soundness / License headers check	7s
Soundness / Shell check	32s
Unit tests / Unit tests / Linux (5.8)	24s
Unit tests / Unit tests / Linux (5.9)	1m 35s
Unit tests / Unit tests / Linux (5.10)	1m 30s
Unit tests / Unit tests / Linux (nightly-6.0)	2m 11s
Unit tests / Unit tests / Linux (nightly-main)	32s
	1h 16m 51s

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