Smart indentation on separated elements should reuse the prior element's starting base indentation

Consider what I'd call some "ideal" smart indentation for the following code samples:

type Foo =
    | "hello"
    | "world";

{| "indentation": 0 |}

let x = 10,
    y = 2;
{| "indentation": 0 |}

let x = 10,
    y = 2,
    {| "indentation": 4 |}

let obj = {
    x: "hello" +
        "world",
    {| "indentation": 4 |}
}

class C {
    x = "hello" +
        "world";
    {| "indentation": 4 |}
}

I've specified the "expected" indentation in each of these cases; however, TypeScript today keeps indentation are the same level as the prior line which is wrong. This is especially annoying for the multi-line union case.

There is some ambiguity when one uses an ASI-assuming style though. In these cases, I would personally err on the side of expecting the start indentation.

type Foo =
| "hello"
| "world"
{| "indentation": 0 |}

```ts
let x = 10,
    y = 2
{| "indentation": 0 |}

class C {
    x = "hello" +
        "world"
    {| "indentation": 4 |}
}

Then, even for cases where ASI doesn't really apply:

let obj = {
    x: "hello" +
        "world"
    {| "indentation": 4 |}
}

I would say we should pick the start element's base (where x starts), since we'll start doing #52899 eventually.

実装ファイルやテストは指定されていません。まず TypeScript のスマートインデントのエントリポイントを特定し、分離されたユニオン、複数行の変数、オブジェクト、クラスの例に対する動作を比較してください。#52899 との関係も確認してください。完了条件は、指定された ASI のケースを含め、例が直前の要素の開始時の基準インデントを使用し、回帰テストのカバレッジがあることです。