### Summary

`ansible-galaxy collection install` makes a lot of requests to galaxy.ansible.com and can occasionally hit the rate limit. When that happens, galaxy.ansible.com will return a 520 http code and `ansible-galaxy` fails to download the collection and exits. Ideally when the client encounters a rate limiting http code (either 520, or 429), it should wait, slow down the request rate and try again rather than exiting.

More information is available here: https://github.com/ansible/galaxy/issues/2429 

### Issue Type

Bug Report

### Component Name

ansible-galaxy

### Ansible Version

```console
$ ansible --version
root@ubuntu-s-1vcpu-1gb-nyc3-01:~# ansible --version
ansible 2.10.7
  config file = None
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python3.8/dist-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 3.8.5 (default, Jan 27 2021, 15:41:15) [GCC 9.3.0]
```


### Configuration

```console
$ ansible-config dump --only-changed
root@ubuntu-s-1vcpu-1gb-nyc3-01:~# ansible-config dump --only-changed
root@ubuntu-s-1vcpu-1gb-nyc3-01:~#
```


### OS / Environment

All

### Steps to Reproduce

Run `ansible-galaxy collection install `amazon.aws`. If your internet is fast enough, this will occasionally fail when galaxy.ansible.com returns a 520 error code.

### Expected Results

Collection should be installed.

### Actual Results

```console
`ansible-galaxy` encounters a 429 or 520 http code and exits.
```


### Code of Conduct

I agree to follow the Ansible Code of Conduct


data = self._call_galaxy(versions_url, error_context_msg=error_context_msg, cache=True)
        except GalaxyError as err:
            if err.http_code != 404:
                raise
            
            return []
        if 'data' in data:
            
            
            
            results_key = 'data'
        else:
            results_key = 'results'
        versions = []
        while True:
            versions += [v['version'] for v in data[results_key]]
            next_link = data
            for path in pagination_path:
                next_link = next_link.get(path, {})
            if not next_link:
                break
            elif relative_link:
                
                
                next_link = versions_url.replace(versions_url_info.path, next_link)
            data = self._call_galaxy(to_native(next_link, errors='surrogate_or_strict'),
                                     error_context_msg=error_context_msg, cache=True)
        self._set_cache()
        return versions