升级fastjson至2.0.43，替换tomcat为undertow

jeecg-module-system/jeecg-system-start/src/main/resources/application-dev.yml

@@ -1,7 +1,12 @@
 server:
   port: 8080
-  tomcat:
-    max-swallow-size: -1
+  undertow:
+    # 平替 tomcat server.tomcat.max-swallow-siz， undertow该值默认为-1
+    #    max-http-post-size: 10MB
+    worker-threads: 16 # 4核CPU标准配置
+    buffers:
+      websocket: 8192 # WebSocket缓冲 以字节为单位，这里设置为8 KB
+      io: 16384 # IO操作缓冲 以字节为单位，这里设置为16 KB
   error:
     include-exception: true
     include-stacktrace: ALWAYS