WIP add support for Folders in slnx project file and skip non C++ projects #20168

Job	Run time
build_cmake (alpine:3.23, false, false)	4m 25s
build_make (ubuntu:25.10)	5m 10s
build_make (alpine:3.23)	5m 51s
build_cmake (ubuntu:24.04, true, true)	2m 40s
build_make (ubuntu:24.04)	2m 50s
build_cmake (ubuntu:25.10, true, true)	2m 54s
	23m 50s

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