`CREATE DATABASE` location

#451 implemented support for `CREATE DATABASE` queries.
It includes two tests for the query.

`Statement::CreateDatabase` has two additional fields: `location` and `managed_location`. The syntax for these is not detailed; neither in the PR, nor anywhere else I can find.

1. Perhaps this could be detailed in the docs
2. Perhaps tests could be added for these fields
3. What is the syntax for these fields?

首先查看 PR #451 和现有的两个 CREATE DATABASE 测试，然后检查 Statement::CreateDatabase，包括其 location 和 managed_location 字段。确定两个字段的语法并记录下来，添加覆盖该语法的测试，以便明确其行为。

由索引模型根据 Issue 内容生成。