Increase test timeout value by 4x
Increase test timeout value by 4x

Seek to avoid spurious test timeouts in Swift CI by
raising limit for individual test execution from 30
seconds to 120 seconds.

apple/swift-corelibs-libdispatch,apple/swift-corelibs-libdispatch,apple/swift-corelibs-libdispatch,apple/swift-corelibs-libdispatch