Make room for more items when toolbars are aligned vertically

[ptsavol]

This PR decreases the Toolbar icon sizes a little bit when toolbars are aligned vertically or horizontally.

In addition, when the toolbars are aligned vertically, there is now room for more items. The toolbar item text is truncated to 14 characters so it should always take just one line. The item text when a toolbar is in horizontal mode has not been changed.

Fixes # 2964

Checklist before merging

• Documentation is up-to-date
• Unit tests have been added/updated accordingly
• Code has been formatted by black & isort
• Unit tests pass

[codecov]

Codecov Report

Attention: Patch coverage is 60.97561% with 16 lines in your changes missing coverage. Please review.

Project coverage is 66.90%. Comparing base (f11d7bb) to head (5635b5c).

Files with missing lines	Patch %	Lines
spinetoolbox/widgets/project_item_drag.py	56.00%	10 Missing and 1 partial ⚠️
spinetoolbox/widgets/toolbars.py	68.75%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2970      +/-   ##
==========================================
- Coverage   66.91%   66.90%   -0.01%     
==========================================
  Files         190      190              
  Lines       37097    37119      +22     
  Branches     6374     6377       +3     
==========================================
+ Hits        24823    24836      +13     
- Misses      10951    10958       +7     
- Partials     1323     1325       +2     

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