### 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


"""
        Gets the collection information from the Galaxy server about a specific Collection.
        :param namespace: The collection namespace.
        :param name: The collection name.
        return: CollectionMetadata about the collection.
        """
        if 'v3' in self.available_api_versions:
            api_path = self.available_api_versions['v3']
            field_map = [
                ('created_str', 'created_at'),
                ('modified_str', 'updated_at'),
            ]
        else:
            api_path = self.available_api_versions['v2']
            field_map = [
                ('created_str', 'created'),
                ('modified_str', 'modified'),
            ]
        info_url = _urljoin(self.api_server, api_path, 'collections', namespace, name, '/')
        error_context_msg = 'Error when getting the collection info for %s.%s from %s (%s)' \
                            % (namespace, name, self.name, self.api_server)
        data = self._call_galaxy(info_url, error_context_msg=error_context_msg)
        metadata = {}
        for name, api_field in field_map:
            metadata[name] = data.get(api_field, None)
        return CollectionMetadata(namespace, name, **metadata)
    @g_connect(['v2', 'v3'])
    def get_collection_version_metadata(self, namespace, name, version):