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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`

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'''Does some quick checks to see if we can poke a hole into the primality of n.
    A result of `False` does **not** mean that the number is prime; it just means
    that we couldn't detect quickly whether it is not prime.
    '''
    if n <= 2:
        return True
    
    if simple_gcd(n, 7799922041683461553249199106329813876687996789903550945093032474868511536164700810) > 1:
        return True
    
    
    return False
python_version = (sys.version_info[0], sys.version_info[1])
if python_version >= (2, 7) or python_version >= (3, 1):
    
    def count_bits(no):
        no = abs(no)
        if no == 0:
            return 0
        return no.bit_length()
else:
    
    def count_bits(no):
        no = abs(no)
        count = 0
        while no > 0:
            no >>= 1
            count += 1
        return count