FEATURE: 头部区域BasicLayout有些不合理，建议增加多个插槽

[ywwsw]

Version

Vben Admin Pro

Description

目前的BasicLayout 自定的插槽太少了，都固定在系统级里面，这里又不敢乱改，更新后肯定要动的！ 比如我想在头部增加点自定义按钮都要去修改源文件！

Proposed Solution

建议增加多个插槽

Alternatives Considered

No response

Additional Context

No response

Validations

• [X] Read the docs
• [X] Ensure the code is up to date. (Some issues have been fixed in the latest version)
• [X] I have searched the existing issues and checked that my issue does not duplicate any existing issues.