Change the algorithm used by Bamboo's KeyPair Generator to Ed25519

The current KeyPair Generator in Bamboo utilises an RSA/2048-bit length host key pair, which needs to be updated due to recent shifts in SSH vendors disabling SHA1 and, consequently, ssh-rsa.

I propose a modification in OneKeyPairGenerator to replace KEY_ALGORITHM_NAME's RSA with Ed25519 and hardcode the KEY_SIZE to 255 bits, as Ed25519 key size is a constant (255).

This update aligns Bamboo with modern cryptographic standards, ensuring the tool's security and efficiency.