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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`

<!--- HINT: You can also paste gist.github.com links for larger files -->

'2.16.840.1.101.3.4.1.2': ('aes-128-cbc', 'AES-128-CBC'),
    '2.16.840.1.101.3.4.1.3': ('aes-128-ofb', 'AES-128-OFB'),
    '2.16.840.1.101.3.4.1.4': ('aes-128-cfb', 'AES-128-CFB'),
    '2.16.840.1.101.3.4.1.5': ('id-aes128-wrap', ),
    '2.16.840.1.101.3.4.1.6': ('aes-128-gcm', 'id-aes128-GCM'),
    '2.16.840.1.101.3.4.1.7': ('aes-128-ccm', 'id-aes128-CCM'),
    '2.16.840.1.101.3.4.1.8': ('id-aes128-wrap-pad', ),
    '2.16.840.1.101.3.4.1.21': ('aes-192-ecb', 'AES-192-ECB'),
    '2.16.840.1.101.3.4.1.22': ('aes-192-cbc', 'AES-192-CBC'),
    '2.16.840.1.101.3.4.1.23': ('aes-192-ofb', 'AES-192-OFB'),
    '2.16.840.1.101.3.4.1.24': ('aes-192-cfb', 'AES-192-CFB'),
    '2.16.840.1.101.3.4.1.25': ('id-aes192-wrap', ),
    '2.16.840.1.101.3.4.1.26': ('aes-192-gcm', 'id-aes192-GCM'),
    '2.16.840.1.101.3.4.1.27': ('aes-192-ccm', 'id-aes192-CCM'),
    '2.16.840.1.101.3.4.1.28': ('id-aes192-wrap-pad', ),
    '2.16.840.1.101.3.4.1.41': ('aes-256-ecb', 'AES-256-ECB'),
    '2.16.840.1.101.3.4.1.42': ('aes-256-cbc', 'AES-256-CBC'),
    '2.16.840.1.101.3.4.1.43': ('aes-256-ofb', 'AES-256-OFB'),
    '2.16.840.1.101.3.4.1.44': ('aes-256-cfb', 'AES-256-CFB'),
    '2.16.840.1.101.3.4.1.45': ('id-aes256-wrap', ),
    '2.16.840.1.101.3.4.1.46': ('aes-256-gcm', 'id-aes256-GCM'),
    '2.16.840.1.101.3.4.1.47': ('aes-256-ccm', 'id-aes256-CCM'),
    '2.16.840.1.101.3.4.1.48': ('id-aes256-wrap-pad', ),
    '2.16.840.1.101.3.4.2': ('nist_hashalgs', ),
    '2.16.840.1.101.3.4.2.1': ('sha256', 'SHA256'),
    '2.16.840.1.101.3.4.2.2': ('sha384', 'SHA384'),
    '2.16.840.1.101.3.4.2.3': ('sha512', 'SHA512'),
    '2.16.840.1.101.3.4.2.4': ('sha224', 'SHA224'),
    '2.16.840.1.101.3.4.2.5': ('sha512-224', 'SHA512-224'),
    '2.16.840.1.101.3.4.2.6': ('sha512-256', 'SHA512-256'),