[SPARK-16380][EXAMPLES] Update SQL examples and programming guide for Python language binding

This PR is based on PR #14098 authored by wangmiao1981.

## What changes were proposed in this pull request?

This PR replaces the original Python Spark SQL example file with the following three files:

- `sql/basic.py`

  Demonstrates basic Spark SQL features.

- `sql/datasource.py`

  Demonstrates various Spark SQL data sources.

- `sql/hive.py`

  Demonstrates Spark SQL Hive interaction.

This PR also removes hard-coded Python example snippets in the SQL programming guide by extracting snippets from the above files using the `include_example` Liquid template tag.

## How was this patch tested?

Manually tested.

Author: wm624@hotmail.com <wm624@hotmail.com>
Author: Cheng Lian <lian@databricks.com>

Closes #14317 from liancheng/py-examples-update.