Refactor lwt and add force_64 option

[jeromekelleher]

Closes #1589

[codecov]

Codecov Report

Merging #1590 (df59a4f) into main (5256bf7) will increase coverage by 0.01%.
The diff coverage is 97.29%.

❗ Current head df59a4f differs from pull request most recent head 0ef9b51. Consider uploading reports for the commit 0ef9b51 to get more accurate results

@@            Coverage Diff             @@
##             main    #1590      +/-   ##
==========================================
+ Coverage   93.60%   93.62%   +0.01%     
==========================================
  Files          27       27              
  Lines       23036    23074      +38     
  Branches     1079     1079              
==========================================
+ Hits        21562    21602      +40     
+ Misses       1440     1438       -2     
  Partials       34       34              

Flag	Coverage Δ
c-tests	91.85% <ø> (ø)
lwt-tests	93.40% <97.29%> (+0.43%)	⬆️
python-c-tests	95.33% <97.29%> (+0.03%)	⬆️
python-tests	98.80% <ø> (ø)

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Impacted Files	Coverage Δ
python/lwt_interface/tskit_lwt_interface.h	95.41% <97.29%> (+0.36%)	⬆️
python/_tskitmodule.c	91.84% <0.00%> (-0.01%)	⬇️

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[benjeffery]

Looks good, refactoring is an improvement! I assume we don't need an issue to track the logic flip as it is going to error out.

[benjeffery]

By this comment you mean the whole logic of this section will be flipped? I think I get it!

[jeromekelleher]

Yeah, exactly.