[DTS] Object literal method with bigint is omitted in generated `.d.ts`, but class method works correctly

@johnfav03 がすでに取り組んでいます。

2025年8月6日 から。

### 🔎 Search Terms

- dts
- bigint key
- object
- class

### 🕗 Version & Regression Information

- This changed between versions ______ and _______
- This changed in commit or PR _______
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________
- I was unable to test this on prior versions because _______

### ⏯ Playground Link

https://www.typescriptlang.org/play/?#code/KYDwDg9gTgLgBAYwgOwM7wGYQnAvHAbwCg5S4BGZACgEpCSzGpgYBXKZCgbgdIF8ANLzgAmWvUZMW7TiJ6M+RRUVCRYiADYBDVKjgAxbBLKVxxSWWZsO3YYsZi65i3CszR8sor5A

### 💻 Code

```TypeScript
export const foo = {
1n() {
return 1;
},
2() {
return 2;
}
}

export class Foo {
1n() {
return 1;
}
2() {
return 2;
}
}
```

### 🙁 Actual behavior

```TypeScript
export declare const foo: {
2(): number;
};
export declare class Foo {
1n(): number;
2(): number;
}
```

### 🙂 Expected behavior

```TypeScript
export declare const foo: {
1n(): number;
2(): number;
};
export declare class Foo {
1n(): number;
2(): number;
}
```

### Additional information about the issue

_No response_