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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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privatekey = self._load_privatekey()
        if isinstance(privatekey, cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey):
            return self.type == 'RSA' and self.size == privatekey.key_size
        if isinstance(privatekey, cryptography.hazmat.primitives.asymmetric.dsa.DSAPrivateKey):
            return self.type == 'DSA' and self.size == privatekey.key_size
        if CRYPTOGRAPHY_HAS_X25519 and isinstance(privatekey, cryptography.hazmat.primitives.asymmetric.x25519.X25519PrivateKey):
            return self.type == 'X25519'
        if CRYPTOGRAPHY_HAS_X448 and isinstance(privatekey, cryptography.hazmat.primitives.asymmetric.x448.X448PrivateKey):
            return self.type == 'X448'
        if CRYPTOGRAPHY_HAS_ED25519 and isinstance(privatekey, cryptography.hazmat.primitives.asymmetric.ed25519.Ed25519PrivateKey):
            return self.type == 'Ed25519'
        if CRYPTOGRAPHY_HAS_ED448 and isinstance(privatekey, cryptography.hazmat.primitives.asymmetric.ed448.Ed448PrivateKey):
            return self.type == 'Ed448'
        if isinstance(privatekey, cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePrivateKey):
            if self.type != 'ECC':
                return False
            if self.curve not in self.curves:
                return False
            return self.curves[self.curve]['verify'](privatekey)
        return False
    def dump(self):
        """Serialize the object into a dictionary."""
        result = super(PrivateKeyCryptography, self).dump()
        result['type'] = self.type
        if self.type == 'ECC':
            result['curve'] = self.curve
        return result
def main():