Introduce ExcludeFromSourceOnlyBuild control

[mmitche]

See https://microsoft-my.sharepoint.com/:w:/p/mmitche/EdchH8A4okpOoKhkki1sJEYB0LyAaaCyX5_6A887gL744Q?e=JERvht for full design:

When “true” and DotNetBuild == “true” and DotNetBuildSourceOnly == “true” the project is not built.
This is equivalent to ExcludeFromBuild being set to true when DotNetBuild == “true”. Same as ExcludeFromSourceBuild today.
This control applies to project properties.

See locations where ExcludeFromVerticalBuild/SourceBuild exist today.