Auto fixable quick fixes

VS Code is investigating the concept of autofixable quick fixes. You can find the current proposal [here](https://github.com/Microsoft/vscode/issues/62110#issuecomment-454182230) ## Motivating use case You open the following TS file: ```ts interface IFoo { bar(): void; } class Foo implements IFoo { } new foo() ``` This file has two errors: incorrect interface implementation on `class Foo` and a spelling error in `new foo()` You hit `F8` to start navigating through errors. While navigating, you can hit a single keyboard shortcut to auto implement the interface or to correct `foo` -> `Foo` ## Current VS Code proposal To implement auto fixes, VS Code [currently proposes](https://github.com/Microsoft/vscode/issues/62110#issuecomment-454182230) that some quick fixes be marked with a `canAutoApply` flag. This flag would indicate that: - The quick fix will fix the underlying problem (and not suppress it or hide it) - The quick fix can be fairly safely automatically applied without user input - The provider of the quick fix is relatively confident that the quick fix could be correct (100% confidence is not required since the auto fix is being triggered by a user action). More importantly, the quick fix should be easy to undo if it is incorrect When the user hits `auto fix` in VS Code, if only a single `canAutoApply` quick fix is returned for a diagnostic, VS Code would automatically apply it. If multiple `canAutoApply` fixes are returned, we would show a list of these for the user to select from. The existing, more complete list of quick fixes and code actions could still be accessed using the lightbulb menu ## Proposal for TS The UX experience of being able to auto fix errors with a single keyboard shortcut is very nice and I think we can make reasonable fix assumptions about a fair number of real world errors. The work that would be required on the TS side to support the proposed auto fix feature in VS Code: - Add an optional `canAutoApply` property on the TS `CodeFi…