### 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
Object.entries(axiosFactory).forEach(([key, value]) => {
      if(!utils.hasOwnProp(Axios, key) && !(key in instance) && ignoreList.indexOf(key) === -1) {
        factoryExport[key] = value;
      }
    });
    Object.entries(axios).forEach(([key, value]) => {
      key!=='default' && ignoreList.indexOf(key) === -1 && (namedExport[key] = value);
    });
    assert.deepStrictEqual(namedExport, factoryExport);
  });
  describe('CommonJS', ()=> {
    const pkgPath = path.join(__dirname, './cjs');
    after(async ()=> {
      await remove(path.join(pkgPath, './node_modules'));
    });
    it('should be able to be loaded with require', async function () {
      this.timeout(30000);
      await exec(`npm test --prefix ${pkgPath}`);
    });
  });
  describe('ESM', ()=> {
    const pkgPath = path.join(__dirname, './esm');
    after(async ()=> {
      await remove(path.join(pkgPath, './node_modules'));
    });
    it('should be able to be loaded with import', async function () {
      this.timeout(30000);
      await exec(`npm test --prefix ${pkgPath}`);
    });
  });