Tests

Support arbitrary messaging from external loaders #946

Job	Run time
osx	6m 5s
linux (swift:5.8-bionic)	3m 39s
linux (swift:5.8-focal)	3m 59s
linux (swift:5.8-jammy)	5m 23s
linux (swift:5.8-amazonlinux2)	4m 21s
linux (swift:5.9-focal)	5m 5s
linux (swift:5.9-jammy)	4m 8s
linux (swift:5.9-amazonlinux2)	4m 44s
linux (swift:5.10-focal)	3m 58s
linux (swift:5.10-jammy)	4m 1s
linux (swift:5.10-amazonlinux2)	3m 58s
linux (swiftlang/swift:nightly-bionic)	4m 5s
linux (swiftlang/swift:nightly-focal)	4m 5s
linux (swiftlang/swift:nightly-jammy)	4m 9s
linux (swiftlang/swift:nightly-amazonlinux2)	4m 22s
	1h 6m 2s

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