Enable Swift 6 support #19

Job	Run time
Unit tests / Unit tests (swift:5.9-jammy, 5.9, true)	4m 34s
Unit tests / Unit tests (swift:5.10-jammy, 5.10, true)	3m 8s
Unit tests / Unit tests (swift:6.0-jammy, 6.0, true)	3m 36s
Unit tests / Unit tests (swiftlang/swift:nightly-6.0-jammy, nightly-6.0, true)	3m 51s
Unit tests / Unit tests (swiftlang/swift:nightly-main-jammy, nightly-main, true)	4m 6s
Cxx interop / Linux (5.9)	2m 6s
Cxx interop / Linux (5.10)	2m 3s
Cxx interop / Linux (6.0)	2m 32s
Cxx interop / Windows (6.0)	3s
Cxx interop / Linux (nightly-6.0)	2m 47s
Cxx interop / Windows (nightly-6.0)	3s
Cxx interop / Linux (nightly-main)	2m 51s
Cxx interop / Windows (nightly-main)	2s
Soundness / API breakage check	0s
Soundness / Broken symlinks check	5s
Soundness / Documentation check	0s
Soundness / Format check	40s
Soundness / License headers check	8s
Soundness / Shell check	39s
Soundness / Unacceptable language check	6s
Soundness / YAML lint check	5s
Soundness / Python lint check	10s
	33m 35s

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