<!--- Verify first that your feature was not already discussed on GitHub -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### 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 -->

'2.16.840.1.101.3.4.2.7': ('sha3-224', 'SHA3-224'),
    '2.16.840.1.101.3.4.2.8': ('sha3-256', 'SHA3-256'),
    '2.16.840.1.101.3.4.2.9': ('sha3-384', 'SHA3-384'),
    '2.16.840.1.101.3.4.2.10': ('sha3-512', 'SHA3-512'),
    '2.16.840.1.101.3.4.2.11': ('shake128', 'SHAKE128'),
    '2.16.840.1.101.3.4.2.12': ('shake256', 'SHAKE256'),
    '2.16.840.1.101.3.4.2.13': ('hmac-sha3-224', 'id-hmacWithSHA3-224'),
    '2.16.840.1.101.3.4.2.14': ('hmac-sha3-256', 'id-hmacWithSHA3-256'),
    '2.16.840.1.101.3.4.2.15': ('hmac-sha3-384', 'id-hmacWithSHA3-384'),
    '2.16.840.1.101.3.4.2.16': ('hmac-sha3-512', 'id-hmacWithSHA3-512'),
    '2.16.840.1.101.3.4.3': ('dsa_with_sha2', 'sigAlgs'),
    '2.16.840.1.101.3.4.3.1': ('dsa_with_SHA224', ),
    '2.16.840.1.101.3.4.3.2': ('dsa_with_SHA256', ),
    '2.16.840.1.101.3.4.3.3': ('dsa_with_SHA384', 'id-dsa-with-sha384'),
    '2.16.840.1.101.3.4.3.4': ('dsa_with_SHA512', 'id-dsa-with-sha512'),
    '2.16.840.1.101.3.4.3.5': ('dsa_with_SHA3-224', 'id-dsa-with-sha3-224'),
    '2.16.840.1.101.3.4.3.6': ('dsa_with_SHA3-256', 'id-dsa-with-sha3-256'),
    '2.16.840.1.101.3.4.3.7': ('dsa_with_SHA3-384', 'id-dsa-with-sha3-384'),
    '2.16.840.1.101.3.4.3.8': ('dsa_with_SHA3-512', 'id-dsa-with-sha3-512'),
    '2.16.840.1.101.3.4.3.9': ('ecdsa_with_SHA3-224', 'id-ecdsa-with-sha3-224'),
    '2.16.840.1.101.3.4.3.10': ('ecdsa_with_SHA3-256', 'id-ecdsa-with-sha3-256'),
    '2.16.840.1.101.3.4.3.11': ('ecdsa_with_SHA3-384', 'id-ecdsa-with-sha3-384'),
    '2.16.840.1.101.3.4.3.12': ('ecdsa_with_SHA3-512', 'id-ecdsa-with-sha3-512'),
    '2.16.840.1.101.3.4.3.13': ('RSA-SHA3-224', 'id-rsassa-pkcs1-v1_5-with-sha3-224'),
    '2.16.840.1.101.3.4.3.14': ('RSA-SHA3-256', 'id-rsassa-pkcs1-v1_5-with-sha3-256'),
    '2.16.840.1.101.3.4.3.15': ('RSA-SHA3-384', 'id-rsassa-pkcs1-v1_5-with-sha3-384'),
    '2.16.840.1.101.3.4.3.16': ('RSA-SHA3-512', 'id-rsassa-pkcs1-v1_5-with-sha3-512'),
    '2.16.840.1.113730': ('Netscape Communications Corp.', 'Netscape'),
    '2.16.840.1.113730.1': ('Netscape Certificate Extension', 'nsCertExt'),
    '2.16.840.1.113730.1.1': ('Netscape Cert Type', 'nsCertType'),