[FEATURE] Write query string in metadata cache for MV

[seankao-az]

For MV index, add a query string field into metadata cache.

{
      "_meta": {
        "properties": {
          "refreshInterval": 900,
          "sourceTables": [
            "datasource.database.table"
          ],
          "sourceQuery": "SELECT * FROM datasource.database.table",
          "metadataCacheVersion": "1.0",
          "lastRefreshTime": 1234567890123
        }
      },
      "properties": {
        ...
      }
}

What alternatives have you considered?
This will deprioritize / remove the need for #931