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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 -->

'2.5.29.14': ('X509v3 Subject Key Identifier', 'subjectKeyIdentifier'),
    '2.5.29.15': ('X509v3 Key Usage', 'keyUsage'),
    '2.5.29.16': ('X509v3 Private Key Usage Period', 'privateKeyUsagePeriod'),
    '2.5.29.17': ('X509v3 Subject Alternative Name', 'subjectAltName'),
    '2.5.29.18': ('X509v3 Issuer Alternative Name', 'issuerAltName'),
    '2.5.29.19': ('X509v3 Basic Constraints', 'basicConstraints'),
    '2.5.29.20': ('X509v3 CRL Number', 'crlNumber'),
    '2.5.29.21': ('X509v3 CRL Reason Code', 'CRLReason'),
    '2.5.29.23': ('Hold Instruction Code', 'holdInstructionCode'),
    '2.5.29.24': ('Invalidity Date', 'invalidityDate'),
    '2.5.29.27': ('X509v3 Delta CRL Indicator', 'deltaCRL'),
    '2.5.29.28': ('X509v3 Issuing Distribution Point', 'issuingDistributionPoint'),
    '2.5.29.29': ('X509v3 Certificate Issuer', 'certificateIssuer'),
    '2.5.29.30': ('X509v3 Name Constraints', 'nameConstraints'),
    '2.5.29.31': ('X509v3 CRL Distribution Points', 'crlDistributionPoints'),
    '2.5.29.32': ('X509v3 Certificate Policies', 'certificatePolicies'),
    '2.5.29.32.0': ('X509v3 Any Policy', 'anyPolicy'),
    '2.5.29.33': ('X509v3 Policy Mappings', 'policyMappings'),
    '2.5.29.35': ('X509v3 Authority Key Identifier', 'authorityKeyIdentifier'),
    '2.5.29.36': ('X509v3 Policy Constraints', 'policyConstraints'),
    '2.5.29.37': ('X509v3 Extended Key Usage', 'extendedKeyUsage'),
    '2.5.29.37.0': ('Any Extended Key Usage', 'anyExtendedKeyUsage'),
    '2.5.29.46': ('X509v3 Freshest CRL', 'freshestCRL'),
    '2.5.29.54': ('X509v3 Inhibit Any Policy', 'inhibitAnyPolicy'),
    '2.5.29.55': ('X509v3 AC Targeting', 'targetInformation'),
    '2.5.29.56': ('X509v3 No Revocation Available', 'noRevAvail'),
    '2.16.840.1.101.3': ('csor', ),
    '2.16.840.1.101.3.4': ('nistAlgorithms', ),
    '2.16.840.1.101.3.4.1': ('aes', ),
    '2.16.840.1.101.3.4.1.1': ('aes-128-ecb', 'AES-128-ECB'),