Check for provided usings

Implicit using statements makes working with addins in Cake Frosting much simpler. It would be nice to have an analyzer which would suggest this.

Start by reviewing the repository and the issue's reference to implicit using statements, then determine which Cake Frosting add-in scenarios the analyzer should cover. No files, tests, or entry points are identified, so the expected diagnostics, supported cases, and completion criteria need to be clarified before implementation.

Written by the indexing model from the issue text.