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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 -->

'1.2.840.113549.1.9.16.1.19': ('id-smime-ct-contentCollection', ),
    '1.2.840.113549.1.9.16.1.23': ('id-smime-ct-authEnvelopedData', ),
    '1.2.840.113549.1.9.16.1.27': ('id-ct-asciiTextWithCRLF', ),
    '1.2.840.113549.1.9.16.1.28': ('id-ct-xml', ),
    '1.2.840.113549.1.9.16.2': ('id-smime-aa', ),
    '1.2.840.113549.1.9.16.2.1': ('id-smime-aa-receiptRequest', ),
    '1.2.840.113549.1.9.16.2.2': ('id-smime-aa-securityLabel', ),
    '1.2.840.113549.1.9.16.2.3': ('id-smime-aa-mlExpandHistory', ),
    '1.2.840.113549.1.9.16.2.4': ('id-smime-aa-contentHint', ),
    '1.2.840.113549.1.9.16.2.5': ('id-smime-aa-msgSigDigest', ),
    '1.2.840.113549.1.9.16.2.6': ('id-smime-aa-encapContentType', ),
    '1.2.840.113549.1.9.16.2.7': ('id-smime-aa-contentIdentifier', ),
    '1.2.840.113549.1.9.16.2.8': ('id-smime-aa-macValue', ),
    '1.2.840.113549.1.9.16.2.9': ('id-smime-aa-equivalentLabels', ),
    '1.2.840.113549.1.9.16.2.10': ('id-smime-aa-contentReference', ),
    '1.2.840.113549.1.9.16.2.11': ('id-smime-aa-encrypKeyPref', ),
    '1.2.840.113549.1.9.16.2.12': ('id-smime-aa-signingCertificate', ),
    '1.2.840.113549.1.9.16.2.13': ('id-smime-aa-smimeEncryptCerts', ),
    '1.2.840.113549.1.9.16.2.14': ('id-smime-aa-timeStampToken', ),
    '1.2.840.113549.1.9.16.2.15': ('id-smime-aa-ets-sigPolicyId', ),
    '1.2.840.113549.1.9.16.2.16': ('id-smime-aa-ets-commitmentType', ),
    '1.2.840.113549.1.9.16.2.17': ('id-smime-aa-ets-signerLocation', ),
    '1.2.840.113549.1.9.16.2.18': ('id-smime-aa-ets-signerAttr', ),
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    '1.2.840.113549.1.9.16.2.21': ('id-smime-aa-ets-CertificateRefs', ),
    '1.2.840.113549.1.9.16.2.22': ('id-smime-aa-ets-RevocationRefs', ),
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    '1.2.840.113549.1.9.16.2.25': ('id-smime-aa-ets-escTimeStamp', ),