Implement GDExtension support #135

Job	Run time
🧪 Unit tests	26m 22s
cache-env	1s
🍎 macOS / Editor (x86_64, release)	1h 0m 46s
🐧 Linux / Editor (x86_64, release)	33m 46s
🪟 Windows / Editor (x86_64, release)	45m 34s
🐧 Linux / Template (x86_64, release)	23m 21s
🔌 GDExtension / 🐧 Linux (x86_64, release)	57s
🪟 Windows / Editor .NET (x86_64, release)	50m 28s
🔌 GDExtension / 🐧 Linux (x86_64, debug)	55s
🍎 macOS / Editor (arm64, release)	38m 45s
🔌 GDExtension / 🪟 Windows (x86_64, release)	2m 31s
🔌 GDExtension / 🪟 Windows (x86_64, debug)	2m 25s
🔌 GDExtension / 🍎 macOS (universal, release)	54s
🔌 GDExtension / 🍎 macOS (universal, debug)	2m 21s
🍎 macOS / Make macOS Bundles	1m 16s
	4h 50m 22s

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