Adapt to textual 0.87.1

[pablogsal]

The new textual release has some changes:

• There are some changes that we need to do to get the rendered version
  of some textual objects as now render() returns RichVisual instances
• Textual has a new theme so we need to regenerate our snapshots.
• There is something going on with horizontal scroll bars. We have
  opened Horizontal scroll bar disappeared in 0.87.1 Textualize/textual#5284 but looks
  like this may be expected.

Issue number of the reported bug or feature request: #

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[pablogsal]

Note that Textualize/textual#5284 may still be a bug

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.91%. Comparing base (beea5cd) to head (28e31ca).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #698      +/-   ##
==========================================
- Coverage   92.93%   92.91%   -0.03%     
==========================================
  Files          95       95              
  Lines       11655    11656       +1     
  Branches      406      406              
==========================================
- Hits        10832    10830       -2     
- Misses        823      826       +3     

Flag	Coverage Δ
cpp	92.91% <100.00%> (-0.03%)	⬇️
python_and_cython	92.91% <100.00%> (-0.03%)	⬇️

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tests/unit/test_tui_reporter.py:144

• Ensure that the change from widget.render() to widget.renderable is covered by tests to verify the behavior remains correct.

rprint(widget.renderable, file=output)