Rethink fixing by error code and fixName

[andrewbranch]

interface I {}

declare const obj: I;

obj.foo;
//  ^^^ Property 'aa' does not exist on type 'I'.ts(2339)

This error returns two fixes:

For each, the fixName is fixMissingMember. They represent two different ways of fixing the same thing. I believe the current code will try to apply them both. Unfortunately, there’s not actually a way to differentiate them besides their description property, which is dynamic.

A minimal fix, probably good enough to start with, would be to only apply the first fix returned for a given error, since we try to sort the most likely fixes first. If we need more granularity, we’d need an API change from TypeScript itself.