What is the industry term for superset of "metrics" and "dimensions"?
Dimensions and Measures are the two main components of cubes. The dimensions are basically ways to look at the data while the measures are the data.

When writing MDX the measures are a member of the [Measures] dimension but that is mostly a syntax convention.

As for a common name, I would say they both are partly definitions of a cube design. The measures define the values and the dimensions define how you slice or aggregate the measures.

The combined result of a query across dimension members and measures is called a cellset but that term is used for a result rather than a cube definition (which is what measures and dimensions are).

If there even is a common term for the combination of dimensions and measures it would be physical aspects of data aggregation

If I were to design a UI where I list both in an interface for users to add a report I would probably call them 'report items' or 'data components'  or something but I think the clearest for an end user would be to follow  what Excel does and label them 'rows' or 'columns' and 'values' where things you can add to rows/columns are the dimensions and values are the measures.

I don't think it's any clearer to an end user to try and find a common name and from a UI design perspective I would make a distinction between things they should put on an axis and 'values'.