Fix CI4/CI3 encryption compatibility

- Removed the CI3 Encryption library as it's no longer needed.
- Added a field to \App\Config\Encryption.php to allow cipher.
- Removed test code for CI3 encryption and added test code for CI4 decryption of CI3 data.

app/Config/Encryption.php

@@ -57,7 +57,15 @@ class Encryption extends BaseConfig
      */
     public string $digest = 'SHA512';
 
-    /**
+	/**
+	 * The cipher to use.
+	 * This setting is only used by OpenSSLHandler.
+	 *
+	 * Set to aes-128-cbc for CI3 Encryption compatibility.
+	 */
+	public string $cipher = 'aes-256-ctr';
+
+	/**
      * Whether the cipher-text should be raw. If set to false, then it will be base64 encoded.
      * This setting is only used by OpenSSLHandler.
      *