Feature Statistics: Rename to Variable Statistics

[janezd]

Issue

Closes #7084.

Description of changes

• Rename Feature Statistics to Variable Statistics.
• Rename the column from "Name" to "Variable" in the Variable Statistics table.
• Rename the output variable from "Feature" to "Variable".

Backward compatibility (non-)issues:

• Renaming the output variable will break existing workflows that ... huh, that ... filtered by this variable?! Such workflows are unlikely, and the fix would introduce some ugly code, so let us not worry about it.
• Since only the name (and not the qualified name) has changed, existing workflows won't be affected.
• I added a keyword so that typing "feature" still finds the widget.

To do:

• Change documentation ... after the change is confirmed and I (re-)discover how to properly clone the new repo. :)

Includes

• [X] Code changes
• [ ] Documentation

[markotoplak]

Column Statistics?

[wvdvegte]

Column Statistics would also be better than Feature Statistics

[janezd]

Decision: Column.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 88.82%. Comparing base (15e050a) to head (579951f). :warning: Report is 7 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7085   +/-   ##
=======================================
  Coverage   88.82%   88.82%           
=======================================
  Files         335      335           
  Lines       73963    73971    +8     
=======================================
+ Hits        65695    65703    +8     
  Misses       8268     8268           

:rocket: New features to boost your workflow:

• :snowflake: Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[lanzagar]

Merging, but the description has an open To do: documentation, that should not be forgotten. Since the widget name itself was changed, it will be hard to find the right docs for new users https://github.com/biolab/orange3-doc-visual-programming/blob/master/source/widgets/data/featurestatistics.md