Drop Embedded Swift with 6.1 and earlier and remove `JAVASCRIPTKIT_EXPERIMENTAL_EMBEDDED_WASM` #1603

Job	Run time
Build for native target (macos-15, Xcode_16.4)	37s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	44s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	43s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.0.2-release/ubuntu2204/swift-6.0...	39s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	40s
format	31s
build-examples	41s
deploy-examples	1s
	4m 36s

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