See microsoft/TypeScript#22204

We need to support the new suggest diagnostics level from TypeScript. These diagnostics will be used to show places where a refactoring style code fix is available, such as convert es5 function to es6 class. We can also use these to indicate potential problems in files even if these are not errors or warnings, such as marking unused local even when noUnusedLocals is not set

This work item covers both the adoption of ts suggestion diagnostics plus the UX work on the vscode side to make sure we present these diagnostics well