Add support for rsa-sha2-256 and rsa-sha2-512 key algorithms

As announced in OpenSSH 8.2, the ssh-rsa key algorithm is being deprecated due to weaknesses in SHA-1. To continue supporting RSA keys, use of rsa-sha2-256 or rsa-sha2-512 key algorithms as specified in RFC 8332 needs to be added to Trilead.

Alternatively, SSH Build Agents should migrate to using Apache SSH which is actively maintained, supports these key algorithms, and is overall more modern.