BridgeJS: Move optional JSObject to stack ABI, enabling Optional<@JSClass> #2617

Job	Run time
format	34s
Build for native target (macos-15, Xcode_16.4)	2m 12s
build-examples	19m 26s
prettier	10s
check-bridgejs-generated	2m 47s
Test BridgeJS against Swift versions (swift:6.1.2, 601.0.0)	3m 6s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	13m 3s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	12m 12s
Test BridgeJS against Swift versions (swift:6.3, 603.0.0)	3m 20s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	12m 52s
Test BridgeJS against Swift versions (swift:6.2, 602.0.0)	3m 8s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	16m 49s
deploy-examples	0s
	1h 29m 39s

Provide feedback