Closes #33703

`template_string` consists of `template_substitution` and
`string_fragment` chunks. `template_substitution` should not be
considered a string.

```ts
const variable = `this is a string_fragment but ${this.is.template_substitution}`;
```

Release Notes:

- Fixed auto-complete not showing on typing `.` character in template
literal string in JavaScript and TypeScript files.