Refinements to display_violinplot_thicket Function

[Yejashi]

This PR improves the display_violinplot_thicket function in two ways:

• Changed default xlabel to 'thicket' for clarity.

• Restricted function to accept only the same node across all provided thickets.

[ilumsden]

Most of this looks good, but there are two main issues that need to be addressed before I can approve.

[ilumsden]

@Yejashi please rebase this PR on #160 or rebase on develop after #160 is merged. There is a bug in the re-exports of display_violinplot.py that is addressed by #160. If you do not merge the changes from this PR, you will reintroduce the bug.

[ilumsden]

This looks good. @pearce8 just don't merge until my comment regarding #160 is addressed

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.19%. Comparing base (9c53fd9) to head (d829771).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #156      +/-   ##
===========================================
+ Coverage    80.15%   80.19%   +0.03%     
===========================================
  Files           52       52              
  Lines         3442     3448       +6     
===========================================
+ Hits          2759     2765       +6     
  Misses         683      683              

Files	Coverage Δ
thicket/stats/display_violinplot.py	65.53% <100.00%> (+0.59%)	⬆️
thicket/tests/test_display.py	100.00% <100.00%> (ø)