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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 -->

'1.2.840.113549.1.9.16.2.26': ('id-smime-aa-ets-certCRLTimestamp', ),
    '1.2.840.113549.1.9.16.2.27': ('id-smime-aa-ets-archiveTimeStamp', ),
    '1.2.840.113549.1.9.16.2.28': ('id-smime-aa-signatureType', ),
    '1.2.840.113549.1.9.16.2.29': ('id-smime-aa-dvcs-dvc', ),
    '1.2.840.113549.1.9.16.2.47': ('id-smime-aa-signingCertificateV2', ),
    '1.2.840.113549.1.9.16.3': ('id-smime-alg', ),
    '1.2.840.113549.1.9.16.3.1': ('id-smime-alg-ESDHwith3DES', ),
    '1.2.840.113549.1.9.16.3.2': ('id-smime-alg-ESDHwithRC2', ),
    '1.2.840.113549.1.9.16.3.3': ('id-smime-alg-3DESwrap', ),
    '1.2.840.113549.1.9.16.3.4': ('id-smime-alg-RC2wrap', ),
    '1.2.840.113549.1.9.16.3.5': ('id-smime-alg-ESDH', ),
    '1.2.840.113549.1.9.16.3.6': ('id-smime-alg-CMS3DESwrap', ),
    '1.2.840.113549.1.9.16.3.7': ('id-smime-alg-CMSRC2wrap', ),
    '1.2.840.113549.1.9.16.3.8': ('zlib compression', 'ZLIB'),
    '1.2.840.113549.1.9.16.3.9': ('id-alg-PWRI-KEK', ),
    '1.2.840.113549.1.9.16.4': ('id-smime-cd', ),
    '1.2.840.113549.1.9.16.4.1': ('id-smime-cd-ldap', ),
    '1.2.840.113549.1.9.16.5': ('id-smime-spq', ),
    '1.2.840.113549.1.9.16.5.1': ('id-smime-spq-ets-sqt-uri', ),
    '1.2.840.113549.1.9.16.5.2': ('id-smime-spq-ets-sqt-unotice', ),
    '1.2.840.113549.1.9.16.6': ('id-smime-cti', ),
    '1.2.840.113549.1.9.16.6.1': ('id-smime-cti-ets-proofOfOrigin', ),
    '1.2.840.113549.1.9.16.6.2': ('id-smime-cti-ets-proofOfReceipt', ),
    '1.2.840.113549.1.9.16.6.3': ('id-smime-cti-ets-proofOfDelivery', ),
    '1.2.840.113549.1.9.16.6.4': ('id-smime-cti-ets-proofOfSender', ),
    '1.2.840.113549.1.9.16.6.5': ('id-smime-cti-ets-proofOfApproval', ),
    '1.2.840.113549.1.9.16.6.6': ('id-smime-cti-ets-proofOfCreation', ),
    '1.2.840.113549.1.9.20': ('friendlyName', ),
    '1.2.840.113549.1.9.21': ('localKeyID', ),
    '1.2.840.113549.1.9.22': ('certTypes', ),