[Improvement] UI not reporting why table definition is invalid

When editing an existing Pinot table, if the configuration is invalid a popup will be shown that the definition is invalid but the message does not indicate why.

A current workaround exists using the swagger API `POST/tables/validate` endpoint. This endpoint should be called by the UI before submitting the new table definition to validate whether the definition is correct and if not inform the user.

This was found in Pinot v0.7.1

Start by tracing the UI flow that shows the invalid table-definition popup and the Swagger API POST /tables/validate endpoint described in the issue. Done means the UI validates the new table definition before submission and reports why it is invalid.

Written by the indexing model from the issue text.