Tons of exception messages appear when using the new extension syntax

**Version Used**:
Latest Visual Studio Insiders (Insiders [11811.120])
**Steps to Reproduce**:

Every time I use the new extension syntax, tons and tons of popups appear about exceptions in analyzers and refactoring providers. It's annoying.

Start by reproducing the issue in Visual Studio Insiders 11811.120 using the new extension syntax and record which analyzer or refactoring-provider exceptions appear. Done means identifying the failing provider or providers and confirming that normal use no longer produces repeated exception popups.

Written by the indexing model from the issue text.