Add base constructor calls to generated dummy dlls

[Panthr75]

Dummy DLLs currently do not export base constructor calls, which can cause exporting issues when using AssetRipper. Because AssetRipper takes every type in the dummy assembly at face value, it ends up not exporting base constructors to MonoScript files, which leads to compiler errors on Scripting Level 2 (Stub methods, fields, enums, etc) in the generated Unity Project.