QuoteStyle not respected for string literal types in implement interface

[mjbvz]

From microsoft/vscode#101219

TypeScript Version: 4.0.0-dev.20200629

Search Terms:

Code
Using "typescript.preferences.quoteStyle": "single"

interface IFoo {
  a(x: 'abc') : void;
}

class Foo implements IFoo {

}

Run implement interface on Foo

Bug:
The parameter value uses double quotes:

class Foo implements IFoo {
  a(x: "abc"): void {
    throw new Error('Method not implemented.');
  }
}

Also, if typescript.preferences.quoteStyle is unset, it would be nice if we used the original quote style for implement interface