Learn CRDB SQL MovR update

[ericharmeling]

#5040
This PR includes the "Learn CockroachDB SQL" MovR update, originally a part of the #5075 PR. I broke it out into a different feature branch because of the conflicts with MSO...

[cockroach-teamcity]

This change is 

[cockroach-teamcity]

Online preview: http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/03b5f55abdea5d446f1de79881996eb593b7e897/

Edited pages:

• v19.2/learn-cockroachdb-sql.md

[cockroach-teamcity]

Online preview: http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/2dfb9d09b084d62d27998bfedbba1187b4f0eb45/

Edited pages:

• v19.2/learn-cockroachdb-sql.md

[ericharmeling]

@jseldess As you can see in the file diff, I crammed in two separate Learn CRDB SQL instructions... One that uses MovR, for the standard 19.2 docs, and one that does not use MovR (it is essentially identical to the 19.1 Learn CRDB SQL page), for managed.

[cockroach-teamcity]

Online preview: http://cockroach-docs-review.s3-website-us-east-1.amazonaws.com/41a0afb84c173ef47df075aeb6a23d192f01f828/

Edited pages:

• v19.2/learn-cockroachdb-sql.md

[jseldess]

There's an argument to be made that, since no content on the page is really shared anymore, it might be fine to split this into 2 files, e.g., learn-cockroachdb-sql.md and managed-learn-cockroachdb.sql.md. But let's leave it as a single file for now.

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @ericharmeling and @jseldess)

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v19.2/learn-cockroachdb-sql.md, line 20 at r1 (raw file):

Do one of the following:

{% include {{page.version.version}}/sql/movr-start.md %}

I have a few ideas about improving this include, but I'll show you in a separate PR.