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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 -->

'1.2.840.113549.2.13': ('hmacWithSHA512-256', ),
    '1.2.840.113549.3.2': ('rc2-cbc', 'RC2-CBC'),
    '1.2.840.113549.3.4': ('rc4', 'RC4'),
    '1.2.840.113549.3.7': ('des-ede3-cbc', 'DES-EDE3-CBC'),
    '1.2.840.113549.3.8': ('rc5-cbc', 'RC5-CBC'),
    '1.2.840.113549.3.10': ('des-cdmf', 'DES-CDMF'),
    '1.3': ('identified-organization', 'org', 'ORG'),
    '1.3.6': ('dod', 'DOD'),
    '1.3.6.1': ('iana', 'IANA', 'internet'),
    '1.3.6.1.1': ('Directory', 'directory'),
    '1.3.6.1.2': ('Management', 'mgmt'),
    '1.3.6.1.3': ('Experimental', 'experimental'),
    '1.3.6.1.4': ('Private', 'private'),
    '1.3.6.1.4.1': ('Enterprises', 'enterprises'),
    '1.3.6.1.4.1.188.7.1.1.2': ('idea-cbc', 'IDEA-CBC'),
    '1.3.6.1.4.1.311.2.1.14': ('Microsoft Extension Request', 'msExtReq'),
    '1.3.6.1.4.1.311.2.1.21': ('Microsoft Individual Code Signing', 'msCodeInd'),
    '1.3.6.1.4.1.311.2.1.22': ('Microsoft Commercial Code Signing', 'msCodeCom'),
    '1.3.6.1.4.1.311.10.3.1': ('Microsoft Trust List Signing', 'msCTLSign'),
    '1.3.6.1.4.1.311.10.3.3': ('Microsoft Server Gated Crypto', 'msSGC'),
    '1.3.6.1.4.1.311.10.3.4': ('Microsoft Encrypted File System', 'msEFS'),
    '1.3.6.1.4.1.311.17.1': ('Microsoft CSP Name', 'CSPName'),
    '1.3.6.1.4.1.311.17.2': ('Microsoft Local Key set', 'LocalKeySet'),
    '1.3.6.1.4.1.311.20.2.2': ('Microsoft Smartcardlogin', 'msSmartcardLogin'),
    '1.3.6.1.4.1.311.20.2.3': ('Microsoft Universal Principal Name', 'msUPN'),
    '1.3.6.1.4.1.311.60.2.1.1': ('jurisdictionLocalityName', 'jurisdictionL'),
    '1.3.6.1.4.1.311.60.2.1.2': ('jurisdictionStateOrProvinceName', 'jurisdictionST'),
    '1.3.6.1.4.1.311.60.2.1.3': ('jurisdictionCountryName', 'jurisdictionC'),
    '1.3.6.1.4.1.1466.344': ('dcObject', 'dcobject'),
    '1.3.6.1.4.1.1722.12.2.1.16': ('blake2b512', 'BLAKE2b512'),