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