Add initial task extension conformance coverage (#1734) #3182

Job	Run time
build (windows-latest, Release)	19m 3s
build (macos-latest, Release)	12m 3s
build (macos-latest, Debug)	12m 8s
build (ubuntu-latest, Debug)	12m 27s
build (ubuntu-latest, Release)	12m 18s
build (windows-latest, Debug)	18m 57s
publish-coverage / publish-coverage	49s
	1h 27m 45s

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