### Describe the bug

libraries like axios-mock-adapter define an adapter but in same cases need to access to original adapter.

It was working correctly before as the adapter was always a function.
Now it can be an array of string

Only the method getAdapter() in adapters/adapter.js can allow access to original adapters (xhr and http)
But this method is not exported a all at top level.

Can you export it ? 


### To Reproduce

Try to use axios-mock-adapter plugin with onNoMatch option

### Code snippet

_No response_

### Expected behavior

_No response_

### Axios Version

1.2.1 and upper

### Adapter Version

_No response_

### Browser

_No response_

### Browser Version

_No response_

### Node.js Version

_No response_

### OS

_No response_

### Additional Library Versions

_No response_

### Additional context/Screenshots

_No response_
test/module/typings/esm/index.ts
config.headers.foo = "1";
        config.headers.set('bar', '2');
        config.headers.set({myHeader: "myValue"})
        config.headers = new AxiosHeaders({myHeader: "myValue"});
        config.headers = {...config.headers} as AxiosRequestHeaders;
        return config;
      },
      (error: any) => Promise.reject(error)
  );
}
{
  const config: AxiosRequestConfig = {headers: new AxiosHeaders({foo: 1})};
  axios.get('', {
    headers: {
      bar: 2,
      ...config.headers
    }
  });
}
axios.get('/user', {
  lookup: (hostname: string, opt: object, cb: (err: Error | null, address: string, family: number) => void) => {
    cb(null, '127.0.0.1', 4);
  }
});
axios.get('/user', {
  lookup: (hostname: string, opt: object) => {
    return ['127.0.0.1', 4];
  }
});