1.5.1版本server jar包解压后没有发现mysql8的connector

[suinxinliulang]

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

Ⅰ. Issue Description

seata-server jar包解压后发现没有mysql8的connector

Ⅱ. Describe what happened

下载最新的release版本，打算链接mysql8版本，但是总会报com.mysql.cj.jdbc.Driver找不到。
最后，解压了下jar包发现只有5.1.35版本的connector

Caused by: java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:151)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Unknown Source)
        at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:677)
        ... 35 common frames omitted

Ⅲ. Describe what you expected to happen

希望增加mysql8版本的连接器

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

Ⅴ. Anything else we need to know?

no

Ⅵ. Environment:

• JDK version :
• Seata version:
• OS :
• Others:

[slievrly]

@suinxinliulang #4745