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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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"""Load the specified OpenSSL private key.
    The content can also be specified via content; in that case,
    this function will not load the key from disk.
    """
    try:
        if content is None:
            with open(path, 'rb') as b_priv_key_fh:
                priv_key_detail = b_priv_key_fh.read()
        else:
            priv_key_detail = content
        if backend == 'pyopenssl':
            
            
            
            try:
                result = crypto.load_privatekey(crypto.FILETYPE_PEM,
                                                priv_key_detail,
                                                to_bytes(passphrase or ''))
            except crypto.Error as e:
                if len(e.args) > 0 and len(e.args[0]) > 0:
                    if e.args[0][0][2] in ('bad decrypt', 'bad password read'):
                        
                        if passphrase is not None:
                            raise OpenSSLBadPassphraseError('Wrong passphrase provided for private key!')
                        else:
                            raise OpenSSLBadPassphraseError('No passphrase provided, but private key is password-protected!')
                raise OpenSSLObjectError('Error while deserializing key: {0}'.format(e))
            if check_passphrase: