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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 -->

'1.3.6.1.5.5.7.3.19': ('Ctrl/Provision WAP Termination', 'capwapWTP'),
    '1.3.6.1.5.5.7.3.21': ('SSH Client', 'secureShellClient'),
    '1.3.6.1.5.5.7.3.22': ('SSH Server', 'secureShellServer'),
    '1.3.6.1.5.5.7.3.23': ('Send Router', 'sendRouter'),
    '1.3.6.1.5.5.7.3.24': ('Send Proxied Router', 'sendProxiedRouter'),
    '1.3.6.1.5.5.7.3.25': ('Send Owner', 'sendOwner'),
    '1.3.6.1.5.5.7.3.26': ('Send Proxied Owner', 'sendProxiedOwner'),
    '1.3.6.1.5.5.7.3.27': ('CMC Certificate Authority', 'cmcCA'),
    '1.3.6.1.5.5.7.3.28': ('CMC Registration Authority', 'cmcRA'),
    '1.3.6.1.5.5.7.4': ('id-it', ),
    '1.3.6.1.5.5.7.4.1': ('id-it-caProtEncCert', ),
    '1.3.6.1.5.5.7.4.2': ('id-it-signKeyPairTypes', ),
    '1.3.6.1.5.5.7.4.3': ('id-it-encKeyPairTypes', ),
    '1.3.6.1.5.5.7.4.4': ('id-it-preferredSymmAlg', ),
    '1.3.6.1.5.5.7.4.5': ('id-it-caKeyUpdateInfo', ),
    '1.3.6.1.5.5.7.4.6': ('id-it-currentCRL', ),
    '1.3.6.1.5.5.7.4.7': ('id-it-unsupportedOIDs', ),
    '1.3.6.1.5.5.7.4.8': ('id-it-subscriptionRequest', ),
    '1.3.6.1.5.5.7.4.9': ('id-it-subscriptionResponse', ),
    '1.3.6.1.5.5.7.4.10': ('id-it-keyPairParamReq', ),
    '1.3.6.1.5.5.7.4.11': ('id-it-keyPairParamRep', ),
    '1.3.6.1.5.5.7.4.12': ('id-it-revPassphrase', ),
    '1.3.6.1.5.5.7.4.13': ('id-it-implicitConfirm', ),
    '1.3.6.1.5.5.7.4.14': ('id-it-confirmWaitTime', ),
    '1.3.6.1.5.5.7.4.15': ('id-it-origPKIMessage', ),
    '1.3.6.1.5.5.7.4.16': ('id-it-suppLangTags', ),
    '1.3.6.1.5.5.7.5': ('id-pkip', ),
    '1.3.6.1.5.5.7.5.1': ('id-regCtrl', ),
    '1.3.6.1.5.5.7.5.1.1': ('id-regCtrl-regToken', ),
    '1.3.6.1.5.5.7.5.1.2': ('id-regCtrl-authenticator', ),