add additional details for OpenSSL-style keys

[kcreyts]

This PR introduces additional columns which use OpenSSL macros to get additional details about PEM keys in user .ssh/ directories.

• "key_length" uses OpenSSL's EVP_PKEY_bits to get the cryptographic length of the cryptosystem to which the private key belongs, in bits. Definition of cryptographic length is specific to cryptosystem.
• "key_security_bits" uses OpenSSL's EVP_PKEY_security_bits to get the number of security bits of the given key (bits of security as defined in NIST SP800-57).
• "key_group_name" uses OpenSSL's EVP_PKEY_get_group_name to get the group of the private key. Supported for a subset of key_types implemented by OpenSSL.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: kcreyts / name: Kyle Creyts (0939c0e, 3342238)

[directionless]

Seems simple, nice. Can you add this to the table integration tests?

[kcreyts]

extended integration testing.

[directionless]

Seems okay to me. Thank you so much!