• I have searched the issues of this repository and believe that this is not a duplicate.

Ⅰ. Issue Description

改造为springboot后，默认端口是9091，而netty端口是8091，netty和web端口没有自动按照偏移量进行生成，导致用户需要关心的端口配置项为2个，未来引入raft后，server之间通信又会增加一个端口配置，导致易用性降低
建议按照偏移量1000的方式在web端口的改动上自动生成，如9091 那么netty端口就自动为8091，无需干预设置
注意事项：
优先尊重环境变量如SEATA_PORT=xxxx,-p xxxx启动时的端口，做好向下兼容，如果用户没有指定那么就按照web的端口自动生成

Ⅱ. Describe what happened

If there is an exception, please attach the exception trace:

Just paste your stack trace here!

Ⅲ. Describe what you expected to happen

Ⅳ. How to reproduce it (as minimally and precisely as possible)

1. xxx
2. xxx
3. xxx

Ⅴ. Anything else we need to know?

Ⅵ. Environment:

• JDK version :
• OS :
• Others: