Units in Grafana Explore

**Why is this needed**: A common use case for me with Grafana Explore is taking queries from existing panels, changing them a bit, and then visualizing them (often for debugging purpose). I tend to do this via the "Open in Explore" button on a panel. One problem with this is that Grafana Explore does not seem to support units in the Y axis, and so units are lost when opening panels in Explore. On a couple of occasions, I have confused myself thinking the Y axis was still in the unit from the panel (i.e. seconds), when in fact it was in a different unit (milliseconds). **What would you like to be added**: Add support for units in Grafana Explore, and units are maintained when opening a panel in Explore view. **Who is this feature for?** [Add information on what kind of user the feature is for.]