Change num_samples and num_tracked_samples to tsk_size_t

[benjeffery]

Fixes #1723

[jeromekelleher]

LGTM!

[codecov]

Codecov Report

Merging #1727 (0c275ca) into main (eac7482) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 0c275ca differs from pull request most recent head 3c09b42. Consider uploading reports for the commit 3c09b42 to get more accurate results

@@            Coverage Diff             @@
##             main    #1727      +/-   ##
==========================================
- Coverage   93.36%   93.36%   -0.01%     
==========================================
  Files          27       27              
  Lines       24239    24236       -3     
  Branches     1093     1089       -4     
==========================================
- Hits        22631    22628       -3     
  Misses       1573     1573              
  Partials       35       35              

Flag	Coverage Δ
c-tests	92.10% <100.00%> (+<0.01%)	⬆️
lwt-tests	89.25% <ø> (ø)
python-c-tests	94.51% <ø> (-0.01%)	⬇️
python-tests	98.75% <ø> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
c/tskit/stats.c	85.15% <ø> (ø)
c/tskit/haplotype_matching.c	95.05% <100.00%> (ø)
c/tskit/trees.c	94.87% <100.00%> (+<0.01%)	⬆️
python/tskit/trees.py	97.82% <0.00%> (-0.02%)	⬇️
c/tskit/tables.c	90.19% <0.00%> (+0.01%)	⬆️

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[benjeffery]

@jeromekelleher Need a non-author approving review here.

[jeromekelleher]

oops, thanks @benjeffery!