Allow schema to be created with JSON config in UI

Currently if you need to add a schema OSS Pinot Console requires you to input each column manually one by one in the UI. In case user already has a JSON config it doesn't allow you to simply paste the contents and get schema created. Workaround is to use the REST API.

Ask is to allow UI to be able to do this by allowing user to paste the JSON content.

cc @xiangfu0

Start in the Pinot Console schema-creation flow and compare the existing manual column form with the REST API schema configuration. The change is complete when users can paste JSON to create a schema in the UI while the current manual flow still works.

Written by the indexing model from the issue text.