[TypeScript] Cancel geterr before any user-invoked operation

[amcasey]

i.e. Extend 558635a from change to requests like completionInfo and completionEntryDetails.

The corresponding TS issue is microsoft/TypeScript#19458.

[ahejlsberg]

FWIW, this issue is really pronounced when you're editing in large files, like src/compiler/checker.ts in the TypeScript repro--which I so happen to do a lot! Statement completion will often take as much as five seconds to show up because TSServer is busy computing an error list that will just be discarded anyway.

I'd really appreciate getting this fixed.

[mjbvz]

To verify:

1. git clone https://github.com/Microsoft/TypeScript.git
2. Open typescript as folder in vscode. Then open the src/compiler/checker.ts file
3. Wait for initial loading of js/ts language features
4. Type something that will produce an error then trigger suggestions
5. Suggestions should be shown relatively quickly

[isidorn]

Suggestions are shown after 0.5s, I take that as realtivly quickly considering the size of the file -> verified