[BridgeJS] Support @JS var declarations for global scope imports #1922

Job	Run time
check-bridgejs-generated	2m 42s
Build for native target (macos-15, Xcode_16.4)	1m 35s
format	33s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	13m 47s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	17m 6s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	12m 45s
build-examples	41m 46s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	12m 51s
deploy-examples	0s
	1h 43m 5s

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