Assign card dues per individual card and not just note level

[miniwa]

Hi! My use case in Anki has me generating more than 1 card for every note in a model. But I also want to make sure the user sees the cards from a specific template before they see any cards generated by the next template.

Currently, this is not possible to do in genanki, as card dues can only be assigned per individual note level. The workaround is to create duplicate notes for each card type, but that leads to lots of duplicate information and is quite clunky to work with.

I tried my best to figure out a way to implement this without murdering your backward compatibility, it's not the cleanest but it does work. If you spot a way to do this with a cleaner API surface I'm all for that.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0fa4f74) 95.41% compared to head (79a0c13) 95.54%.
Report is 3 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #123      +/-   ##
==========================================
+ Coverage   95.41%   95.54%   +0.13%     
==========================================
  Files          11       11              
  Lines         327      337      +10     
==========================================
+ Hits          312      322      +10     
  Misses         15       15              

Files	Coverage Δ
genanki/note.py	97.65% <100.00%> (+0.19%)	⬆️

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