BridgeJS: Support optional @JS struct in imported function signatures #2662

Job	Run time
build-examples	19m 55s
Test BridgeJS against Swift versions (swift:6.2, 602.0.0)	3m 21s
Test BridgeJS against Swift versions (swift:6.1.2, 601.0.0)	3m 1s
Test BridgeJS against Swift versions (swift:6.3, 603.0.0)	3m 17s
check-bridgejs-generated	2m 43s
Build for native target (macos-15, Xcode_16.4)	2m 39s
format	31s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	7m 20s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	14m 12s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	16m 29s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	10m 32s
prettier	13s
deploy-examples	-1s
	1h 24m 12s

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