Transform: adding missing "table"-transform and "series to rows"-transform to Grafana v7-transforms. (#26042)
* Fixed so the merge for table values works as it did before.
* wip
* fixed tests.
* merge tests are green.
* removed unused code and simplify the seriesToRows.
* added time series to rows editor.
* using getFrameDisplayName for the metric value.
* updated description of transforms.
* updated docs.
* fixed according to feedback.
* changed from images to markdown tables for the examples.
* forgot to save :P
