Text Panel: Support render HTML/markdown using templating of data source query response

### Discussed in https://github.com/grafana/grafana/discussions/38358 <div type='discussions-op-text'> ^{Originally posted by **pachico** January 28, 2020} Many times it is necessary to display in Dashboards the content of what in a database would be the columns of a single row: details of a booking, of a node, last point statistics, etc.To do this, we can only use the table panel and put the values one after the other in columnar fashion.This is ok but the space usage and readability are not great. My proposal is to have panel where the content is pure HTML with placeholders that will be interpolated with the values of a single row.Ideally, it could be a repeatable panel, one for each row returned by the data source.   Hope you find this interesting. Cheers</div>