feat: add rate limiting and improve event handling

- Introduced rate limiting configuration in config.toml with options for enabling, requests per second (RPS), and burst capacity.
- Enhanced event handling in the OneBot11 adapter to ignore messages sent by the bot itself.
- Updated the dispatcher to register rate limit middleware based on configuration settings.
- Refactored WebSocket message handling to support flexible JSON parsing and improved event type detection.
- Removed deprecated echo plugin and associated tests to streamline the codebase.

configs/config.toml

@@ -18,6 +18,11 @@ version = "1.0"
 [protocol.options]
 # Protocol specific options can be added here
 
+[engine.rate_limit]
+enabled = true
+rps = 100      # 每秒请求数
+burst = 200    # 突发容量
+
 # ============================================================================
 # Bot 配置
 # ============================================================================