Meta API (`/meta`): Add the `sql_table` field to the response

The [`/v1/meta` API endpoint](https://cube.dev/docs/reference/rest-api#v1meta) does not include the `sql_table` field. Even with the `?extended` query param the `sql_table` field does not exist, even though `sql` does. It would also be great to have this included unless there is a good reason not to.

I believe it's the following function that needs to be adapted along with the unit tests: https://github.com/cube-js/cube/blob/e8d81f2e04ce61215b1185d9adc4320233bc34da/packages/cubejs-api-gateway/src/helpers/transformMetaExtended.ts#L37

I'm happy to open a pull request for the same!