关于 `SHARDING KEY GENERATOR` 的任务清单

[lanchengx]

在 Sharding 特性中 DistSQL 计划对 KeyGenerator 属性进行更完备支持，任务清单如下

1. DistSQL plans to support `CREATE SHARDING KEY GENERATOR` · Issue #13994 · apache/shardingsphere · GitHub
2. Add syntax for `ALTER SHARDING KEY GENERATOR` · Issue #13997 · apache/shardingsphere · GitHub
3. Add syntax for `SHOW SHARDING KEY GENERATORS` · Issue #13998 · apache/shardingsphere · GitHub
4. Add syntax for `DROP SHARDING KEY GENERATOR` · Issue #13999 · apache/shardingsphere · GitHub