TS2Swift: emit enums for string literal unions #2354

Job	Run time
format	30s
prettier	8s
Build for native target (macos-15, Xcode_16.4)	2m 13s
Test BridgeJS against Swift versions (swift:6.2, 602.0.0)	3m 15s
Test BridgeJS against Swift versions (swift:6.1.2, 601.0.0)	2m 59s
check-bridgejs-generated	2m 49s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	13m 9s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	14m 16s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	12m 27s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	14m 16s
build-examples	14m 14s
deploy-examples	1s
	1h 20m 17s

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