Rename spindb_api keyword arguments for consistency

[soininen]

This PR contains the Toolbox side changes of spine-tools/Spine-Database-API#334

Re spine-tools/Spine-Database-API#318

Checklist before merging

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

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (99844fc) 63.72% compared to head (1537bab) 63.72%.
Report is 3 commits behind head on 0.8-dev.

Files	Patch %	Lines
...oolbox/spine_db_editor/widgets/graph_view_mixin.py	0.00%	2 Missing ⚠️
...olbox/spine_db_editor/widgets/add_items_dialogs.py	50.00%	1 Missing ⚠️

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Additional details and impacted files

@@           Coverage Diff            @@
##           0.8-dev    #2482   +/-   ##
========================================
  Coverage    63.72%   63.72%           
========================================
  Files          195      195           
  Lines        35530    35530           
  Branches      6027     6027           
========================================
+ Hits         22642    22643    +1     
+ Misses       11699    11698    -1     
  Partials      1189     1189           

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