[ENH] Distributions: change Histogram Data output

[thocevar]

Issue

Fixes #4813

Description of changes

Data output (annotated data) is always active. Before it was active only when something was selected. There was an explicit test that the output is empty after loading the data (no idea why).

Histogram data output now contains the bin and frequency data that is displayed in the widget. I don't know what was its purpose before (it was almost the same as Data).

Includes

• Code changes
• Tests
• Documentation

[codecov]

Codecov Report

Merging #4832 into master will increase coverage by 0.05%.
The diff coverage is 92.59%.

@@            Coverage Diff             @@
##           master    #4832      +/-   ##
==========================================
+ Coverage   84.02%   84.07%   +0.05%     
==========================================
  Files         281      277       -4     
  Lines       56898    56510     -388     
==========================================
- Hits        47808    47511     -297     
+ Misses       9090     8999      -91     

[ajdapretnar]

This drastically changes the Histogram output. Before it output the data with the selected variable split into bins as set in the widget. --> Btw, this is probably also why it didn't output anything for discrete variables.

I think Data could always be on the output (that is the way elsewhere).

[thocevar]

Information about bins (for distributions of continuous variables) is now included in the Data output besides the selection indicator.

[janezd]

I wanted to add a commit with updated documentation, but then saw that the current documentation is from the period shortly after the elves departed from Middle Earth and needs to be entirely rewritten and rescreenshot.

We should organize an "update the docs" sprint some day.