[SPARK-20067][SQL] Unify and Clean Up Desc Commands Using Catalog Interface

### What changes were proposed in this pull request?

This PR is to unify and clean up the outputs of `DESC EXTENDED/FORMATTED` and `SHOW TABLE EXTENDED` by moving the logics into the Catalog interface. The output formats are improved. We also add the missing attributes. It impacts the DDL commands like `SHOW TABLE EXTENDED`, `DESC EXTENDED` and `DESC FORMATTED`.

In addition, by following what we did in Dataset API `printSchema`, we can use `treeString` to show the schema in the more readable way.

Below is the current way:
```
Schema: STRUCT<`a`: STRING (nullable = true), `b`: INT (nullable = true), `c`: STRING (nullable = true), `d`: STRING (nullable = true)>
```
After the change, it should look like
```
Schema: root
 |-- a: string (nullable = true)
 |-- b: integer (nullable = true)
 |-- c: string (nullable = true)
 |-- d: string (nullable = true)
```

### How was this patch tested?
`describe.sql` and `show-tables.sql`

Author: Xiao Li <gatorsmile@gmail.com>

Closes #17394 from gatorsmile/descFollowUp.

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