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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.

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```yaml
openssl_privatekey:
  path: /etc/ssl/private/ansible.com.pem
  format: pkcs8
```
The values allowed are `pkcs1`, `raw` and `pkcs8`

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'''Computes f^e mod m in O(log e) multiplications modulo m.'''
    
    len_e = -1
    x = e
    while x > 0:
        x >>= 1
        len_e += 1
    
    result = 1
    for k in range(len_e, -1, -1):
        result = (result * result) % m
        if ((e >> k) & 1) != 0:
            result = (result * f) % m
    return result
def simple_gcd(a, b):
    '''Compute GCD of its two inputs.'''
    while b != 0:
        a, b = b, a % b
    return a
def quick_is_not_prime(n):