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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 certificate."""
    try:
        with open(path, 'rb') as cert_fh:
            cert_content = cert_fh.read()
        if backend == 'pyopenssl':
            return crypto.load_certificate(crypto.FILETYPE_PEM, cert_content)
        elif backend == 'cryptography':
            return x509.load_pem_x509_certificate(cert_content, cryptography_backend())
    except (IOError, OSError) as exc:
        raise OpenSSLObjectError(exc)
def load_certificate_request(path, backend='pyopenssl'):