Feature request: easily list/explore all objects (in schema)

In navigating a database with a lot of schemas, and a lot of different type of objects (tables, views, functions, data types, trigger, etc), there is a lot of friction in exploring the database because you have to manually list each type of object. And with schemas, the non-intuitive search path semantics make it extra hard.

I think it would be a great feature if one could just (as a figure of speech) `cd` into a schema and run `ls [-l]`, which would then show everything and what it is.

首先检查 pgcli 当前如何列出表、视图、函数、数据类型和触发器，以及 schema 导航和 search paths 是如何表示的。定义输入一个 schema 后跟 `ls` 或 `ls -l` 时的范围和输出；完成标准是一个命令能够显示所请求的对象类型，并提供有用的类型和详细信息。

由索引模型根据 Issue 内容生成。