Benchmarks: optional-return cases and runner tweaks #1984

Job	Run time
build-examples	43m 29s
Build for native target (macos-15, Xcode_16.4)	2m 14s
format	35s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	13m 9s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	17m 22s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	13m 40s
check-bridgejs-generated	2m 42s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	12m 53s
deploy-examples	-1s
	1h 46m 3s

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