Add IndentedTextWriter type #4295

Job	Run time
build-solution (Debug, x64)	11m 38s
build-solution (Debug, arm64)	16m 40s
build-solution (Release, x64)	18m 48s
build-packages	6m 23s
build-solution (Release, arm64)	21m 46s
verify-packages (net7.0)	2m 29s
verify-packages (net6.0)	9m 33s
verify-packages (net472)	1m 57s
run-tests-win2d (Debug, uwp)	5m 46s
run-tests (net7.0)	10m 7s
run-tests-win2d (Debug, wasdk)	5m 7s
run-tests (net6.0)	9m 40s
run-samples (net7.0)	7m 2s
run-tests-win2d (Release, uwp)	8m 29s
run-samples-aot (x64)	9m 20s
run-tests (net472)	8m 50s
run-samples (net6.0)	3m 59s
run-tests-win2d (Release, wasdk)	9m 7s
run-samples-aot (arm64)	6m 11s
run-samples (net472)	5m 12s
run-tests-d3d12ma (net7.0)	6m 12s
run-tests-d3d12ma (net6.0)	6m 59s
publish-nightlies-github	54s
publish-nightlies-azure-devops	54s
	3h 13m 3s

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