feat(parser): attach all comments to nodes (#25944)

## Summary

Comments are now attached to their adjacent tokens using source boundaries.

A leading comment belongs to the token that follows it:

```js
/* leading */ value
              ^ attached_to
```

A trailing comment belongs to the token that precedes it:

```js
value /* trailing */
     ^ attached_to
```

`Comment::attached_to` now consistently represents either:

- the start of the following token for leading comments;
- the end of the preceding token for trailing comments.