Give 'this' keyword suggestion the same `sortText` as class properties if inside a class

From https://github.com/Microsoft/vscode/issues/66868

TypeScript Version: 3.4.0-dev.20190220

Search Terms:

• suggestions
• completions
• sortText

Code
For the javascript:

class Foo {
    constructor() {
        this.prop = 1;
    }

    render() {
        th
    }
}

• Trigger intellisense after th in render

Expected behavior:
this should be the first suggestion in VS Code

Actual behavior:
render and then prop are the first suggestions

The root cause of this is that the suggestion for this has a sortText of "0" while the one for prop and render have a sortText of "1". This causes VS Code to sort prop and render before this

@amcasey @minestarks I'm not sure if the current sorting issue would also effect VS

Playground Link:

Related Issues:

Riproduci l’ordinamento dei completamenti nel servizio del linguaggio TypeScript usando l’esempio di classe e ispeziona le voci di completamento per this, prop e render. Aggiorna il comportamento di completamento pertinente in modo che this utilizzi lo stesso sortText delle proprietà della classe, quindi aggiungi o aggiorna un test di regressione che copra l’esempio e verifica l’ordinamento risultante.