feat: Initial implementation of many GCD API's using Swift Concurrency #1

Job	Run time
tests / Linux (5.10 - jammy)	29s
tests / Linux (6.1 - jammy)	41s
tests / Linux (6.0 - jammy)	30s
tests / macOS (Xcode ${{ matrix.xcode_version }} - ${{ matrix.os_version }} - ${{ matrix.arch }})	0s
tests / Linux (nightly-main - jammy)	50s
tests / Linux (5.9 - jammy)	28s
tests / Linux (nightly-6.1 - jammy)	50s
tests / Linux (nightly-6.2 - jammy)	48s
tests / Windows (6.0 - windows-2022)	14m 14s
tests / Windows (5.9 - windows-2022)	14m 16s
tests / Windows (nightly - windows-2019)	9m 53s
tests / Windows (6.1 - windows-2022)	14m 25s
tests / Windows (nightly-6.1 - windows-2019)	10m 21s
Soundness / API breakage check	28s
Soundness / Documentation check	45s
Soundness / Shell check	37s
Soundness / Format check	35s
Soundness / Broken symlinks check	6s
Soundness / License headers check	5s
Soundness / YAML lint check	6s
Soundness / Python lint check	7s
Soundness / Unacceptable language check	5s
WebAssembly SDK / WebAssembly SDK / Linux (latest-release)	17s
WebAssembly SDK / WebAssembly SDK / Linux (main Jammy)	18s
	1h 11m 14s

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