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##### SUMMARY
Allow to specify a new "format" parameter in "openssl_privatekey". Today the output format is decided by a very simple heuristic which requires further commands to work properly.
I need, for example, to generate a RSA private key but in PKCS8 format. The current heuristic uses OpenSSH format for RSA keys and only uses PKCS8 for Ed25519 and similar. This makes me use a "command" with "openssl" to convert the generated key, which leads to idempotency problems and unnecessary complexity.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
openssl_privatekey

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->
The current heuristic should be kept unless overwritten by user.

<!--- Paste example playbooks or commands between quotes below -->
```yaml
openssl_privatekey:
  path: /etc/ssl/private/ansible.com.pem
  format: pkcs8
```
The values allowed are `pkcs1`, `raw` and `pkcs8`

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dotted_string = oid.dotted_string
    names = _OID_MAP.get(dotted_string)
    name = names[0] if names else oid._name
    if short:
        return _NORMALIZE_NAMES_SHORT.get(name, name)
    else:
        return _NORMALIZE_NAMES.get(name, name)
def cryptography_get_name(name):
    '''
    Given a name string, returns a cryptography x509.Name object.
    Raises an OpenSSLObjectError if the name is unknown or cannot be parsed.
    '''
    try:
        if name.startswith('DNS:'):
            return x509.DNSName(to_text(name[4:]))
        if name.startswith('IP:'):
            return x509.IPAddress(ipaddress.ip_address(to_text(name[3:])))
        if name.startswith('email:'):
            return x509.RFC822Name(to_text(name[6:]))
        if name.startswith('URI:'):
            return x509.UniformResourceIdentifier(to_text(name[4:]))
    except Exception as e:
        raise OpenSSLObjectError('Cannot parse Subject Alternative Name "{0}": {1}'.format(name, e))
    if ':' not in name:
        raise OpenSSLObjectError('Cannot parse Subject Alternative Name "{0}" (forgot "DNS:" prefix?)'.format(name))
    raise OpenSSLObjectError('Cannot parse Subject Alternative Name "{0}" (potentially unsupported by cryptography backend)'.format(name))
def _get_hex(bytesstr):