Fix [DebuggerDisplay] for Project (#6650)
Fix [DebuggerDisplay] for Project (#6650)

_data was extracted to a ProjectImpl class, so need to add the implementation field first.
sean-gilliam/msbuild,rainersigwald/msbuild,sean-gilliam/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,rainersigwald/msbuild,sean-gilliam/msbuild,AndyGerlicher/msbuild,AndyGerlicher/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild