BridgeJS: support imports of JS `Promise` as `async` Swift #2521

Job	Run time
check-bridgejs-generated	2m 52s
Test BridgeJS against Swift versions (swift:6.1.2, 601.0.0)	3m 0s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	13m 23s
prettier	11s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	18m 24s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	14m 10s
build-examples	20m 30s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	21m 7s
format	37s
Build for native target (macos-15, Xcode_16.4)	2m 59s
Test BridgeJS against Swift versions (swift:6.2, 602.0.0)	3m 6s
deploy-examples	0s
	1h 40m 19s

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