Automate the testing of SQL commands

[jseldess]

Jesse Seldess commented:

We have SQL commands throughout almost all of our tutorials and how-tos (e.g., Learn CockroachDB SQL, SQL Tuning with EXPLAIN, and in examples throughout our SQL reference docs (e.g., CREATE INDEX. Just as with driver/ORM code samples, it'd be ideal to automate the testing of our SQL commands to ensure our docs are accurate and copy/paste-able for users.

Possible actions:

• [ ) Use a consistent dataset (built-in to cockroach) across SQL docs. @ericharmeling and @rmloveland made some initial progress here using the movr dataset built into [cockroach demo](https://www.cockroachlabs.com/docs/stable/cockroach-demo.html] on a subset of SQL docs. We should verify that's the approach we want.
• [ ) Automate the testing of the code on a regular basis via CI. Approach may be the same or different to https://github.com/cockroachdb/docs/issues/7066.

Jira Issue: DOC-485