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:

クラスの例を使って TypeScript language service の補完順序を再現し、this、prop、render の補完エントリを調べます。関連する補完動作を更新し、this がクラスプロパティと同じ sortText を使用するようにしてから、例を対象とするリグレッションテストを追加または更新し、結果の順序を確認します。