Benchmarks: optional-return cases and runner tweaks #1981

Job	Run time
check-bridgejs-generated	2m 46s
Build for native target (macos-15, Xcode_16.4)	3m 7s
build-examples	43m 36s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	12m 40s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	12m 56s
format	32s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	12m 56s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	12m 56s
deploy-examples	0s
	1h 41m 29s

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