Improve testing for StreamableHttpHandler and IdleTrackingBackgroundService #95

Job	Run time
build (macos-latest, Debug)	1m 30s
build (macos-latest, Release)	1m 30s
build (ubuntu-latest, Release)	2m 29s
build (windows-latest, Release)	5m 34s
build (ubuntu-latest, Debug)	2m 52s
build (windows-latest, Debug)	4m 44s
publish-coverage	0s
	18m 39s

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