ark: No description shown for data frames or lists

[jmcphers]

In the Python extension, the Environment implementation shows some information about data frames in the description field; here it's [3 rows x 2 columns] pandas.core.frame.DataFrame:

It also shows a summary for a list:

The R extension does not generate a description for either of these objects; the description is blank for data frames:

and lists:

I think we should show a short summary or description of these items. It's useful to be able to see something before they are expanded, especially if the environment pane becomes narrow enough to cause the type hint to become hidden. This makes the object look empty:

[DavisVaughan]

@romainfrancois this looks reasonable to me. I'm not sure if you want to do more here right now so I'll let you close when you are ready, but consider this QC'd in its current state

One thing to note - For objects with multiple class names, in rlang:::obj_type_friendly() we have recently switched to only showing the first class name because I think that is more useful 99% of the time (note the tibble preview below). So that is something we could consider doing here too. r-lib/rlang#1622

Screen.Recording.2023-06-01.at.1.41.32.PM.mov

[jmcphers]

I think we can consider this closed for alpha. Thanks @romainfrancois & @DavisVaughan!