Summary

As schema api already supports undrop_database operation

https://github.com/datafuselabs/databend/blob/main/common/meta/api/src/schema_api_impl.rs#L268

undrop database statement can be implemented now.

• the syntax:

UNDROP DATABASE <name>

• the "sementics"
  undrop the dropped table ... : -), e.g.

  create database test;
  create table test.tbl (a int);
  drop database test;
  select * from test.tbl; -- expects error 1003, `UnknownDatabase`
  undrop database test;
  select * from test.tbl; -- back to normal

reference:

• Feat : undrop table & show history #5562
• NOTE, unlike the previous PR
  • do not need to implement the show databases history statement
  • and legacy parser(sqlparser-rs) only is OK