DDRITs coverage of VB projects is insufficient

[dmonroym]

Moving this from AzDo AB#832602

PR 171537 broke loading of VB projects but passed DDRITs without issue. We need to add VB project coverage to the DDRITs, or expand existing coverage appropriately. We should also check that a similar break in C# projects would have been caught.

In this case, the VB projects still "loaded" but the project system ended up passing no information to the language service, meaning no Intellisense support. I expect designers would have been broken as well.