Make generate_private_key() and generate_public_key() public

We need this change for server side implementation.
Specifically at Session:new() before a key exchange is performed.

Signed-off-by: Dhanuka Warusadura <dhanuka@gnome.org>

client/src/key.rs

@@ -39,11 +39,11 @@ impl Key {
         Self { key, strength }
     }
 
-    pub(crate) fn generate_private_key() -> Self {
+    pub fn generate_private_key() -> Self {
         Self::new(crypto::generate_private_key().to_vec())
     }
 
-    pub(crate) fn generate_public_key(private_key: &Self) -> Self {
+    pub fn generate_public_key(private_key: &Self) -> Self {
         Self::new(crypto::generate_public_key(private_key))
     }