[SPARK-17910][SQL] Allow users to update the comment of a column

## What changes were proposed in this pull request?

Right now, once a user set the comment of a column with create table command, he/she cannot update the comment. It will be useful to provide a public interface (e.g. SQL) to do that.

This PR implements the following SQL statement:
```
ALTER TABLE table [PARTITION partition_spec]
CHANGE [COLUMN] column_old_name column_new_name column_dataType
[COMMENT column_comment]
[FIRST | AFTER column_name];
```

For further expansion, we could support alter `name`/`dataType`/`index` of a column too.

## How was this patch tested?

Add new test cases in `ExternalCatalogSuite` and `SessionCatalogSuite`.
Add sql file test for `ALTER TABLE CHANGE COLUMN` statement.

Author: jiangxingbo <jiangxb1987@gmail.com>

Closes #15717 from jiangxb1987/change-column.