cli: Improve test utilities

This will allow easy creation of multiple users with deterministic keys.

Signed-off-by: Alexis Sellier <self@cloudhead.io>

radicle-crypto/src/ssh/keystore.rs

@@ -201,8 +201,7 @@ impl MemorySigner {
 
     /// Generate a new memory signer.
     pub fn gen() -> Self {
-        let seed = crate::Seed::generate();
-        let keypair = KeyPair::from_seed(seed);
+        let keypair = KeyPair::generate();
         let sk = keypair.sk;
 
         Self {