### Describe the bug

`AxiosHeaders` types makes it so trying to call methods on the instance raises a `typescript` compilation error.

<img width="1142" alt="image" src="https://user-images.githubusercontent.com/476069/209943677-fa7775e7-0f23-4b86-88ae-ad28df8c0533.png">

`AxiosRequestConfig.headers` can be either `RawAxiosRequestHeaders` or `AxiosHeaders`. `RawAxiosRequestHeaders`, being an alias of `Record<string, AxiosHeaderValue>` causes methods to not be callable.

### To Reproduce

Invoke any method on `AxiosRequestConfig.headers`.

### Code snippet

```js
const api = axios.create({ ... })

api.interceptors.request.use(req => {
  // Trying to access any method on `req.headers` will result in
  // a "This expression is not callable" TS error
  req.headers.set('foo', 'bar')
})
```


### Expected behavior

Should be able to call any method declared in `AxiosHeaders`.

### Environment

* `axios`: `1.2.2`
* `node`: `18.12.1`
* `typescript`: `4.9.4`
* macOS Ventura `13.1` 

test/module/test.js
import assert from 'assert';
import * as axios from '../../index.js';
import axiosFactory from '../../lib/axios.js';
import utils from "../../lib/utils.js";
import {fileURLToPath} from 'url';
import path from 'path';
import util from "util";
import cp from "child_process";
import fs from 'fs-extra';
const BACKUP_PATH = './backup/';
const __dirname = path.dirname(fileURLToPath(import.meta.url));
const exec = util.promisify(cp.exec);
const spawn = (command, args) =>  new Promise((resolve, reject) => {
  cp.spawn(command, args, {
    shell : true,
    stdio: 'inherit'
  }).once('error', reject).on(
    'close',
    (code) => code ? reject(new Error(`Exit code ${code}`)) : resolve()
  );