Do not regenerate aes key pair (#1114)

And read it from `device_config` if provided.

This is required as key generation can eat up cpu when a device is not fully available and the library is retrying.

kasa/aestransport.py

@@ -106,6 +106,9 @@ class AesTransport(BaseTransport):
         self._session_cookie: dict[str, str] | None = None
 
         self._key_pair: KeyPair | None = None
+        if config.aes_keys:
+            aes_keys = config.aes_keys
+            self._key_pair = KeyPair(aes_keys["private"], aes_keys["public"])
         self._app_url = URL(f"http://{self._host}:{self._port}/app")
         self._token_url: URL | None = None
 
@@ -271,7 +274,14 @@ class AesTransport(BaseTransport):
         can be made to the device.
         """
         _LOGGER.debug("Generating keypair")
-        self._key_pair = KeyPair.create_key_pair()
+        if not self._key_pair:
+            kp = KeyPair.create_key_pair()
+            self._config.aes_keys = {
+                "private": kp.get_private_key(),
+                "public": kp.get_public_key(),
+            }
+            self._key_pair = kp
+
         pub_key = (
             "-----BEGIN PUBLIC KEY-----\n"
             + self._key_pair.get_public_key()  # type: ignore[union-attr]
@@ -286,7 +296,6 @@ class AesTransport(BaseTransport):
         """Perform the handshake."""
         _LOGGER.debug("Will perform handshaking...")
 
-        self._key_pair = None
         self._token_url = None
         self._session_expire_at = None
         self._session_cookie = None