VReplication: Improve replication plan error messages

[mattlord]

Description

We did not have documentation covering the limitations of materialization queries used in VReplication workflows. This is primarily a consideration for the Materialize command where you a specify an arbitrary query to materialize in a new table vs. the other workflows (e.g. MoveTables and Reshard) where we're generally copying table data rather than query results.

On top of that, most of the errors resulting from the use of unsupported SQL constructs in Materialize queries did not make it clear what in the query was unsupported. For example:

"Message": "unexpected: select car.id, car.make, car.model, car.`year`, car.mileage, car.price, JSON_ARRAYAGG(json_object('start', booking.start_time, 'end', booking.end_time)) as booked_times from car left join booking on car.id = booking.car_id group by car.id",

The primary cause of the failure above is the JOIN as the big general limitation is that you must use a single table -- this limitation coming from the replication phase where we need to apply binlog events and lack the ability to (easily) maintain the JOIN results when doing so. But because we don't clearly document the limitations and the error is clearly not helpful in that regard, a user would have no idea why things aren't working.

This PR aims to improve the error messages AND serve as the basis for a documentation PR where we lay out the main limitations.

Related Issue(s)

• Fixes: meterialize: Getting 'unexpected error' when making a workflow with sql join query #14749

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests were updated
• Did the new or modified tests pass consistently locally and on the CI
• Documentation: Document query limitations for Materialize website#1653

[vitess-bot]

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[derekperkins]

Big fan of improved error messages