Place result as the last arg in stats API

[benjeffery]

Seemed to make sense to do this before 1.0 even though these are undocumented.
Fixes #2285

[codecov]

Codecov Report

Merging #2292 (b43f0a6) into main (9ce06f0) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2292   +/-   ##
=======================================
  Coverage   93.33%   93.33%           
=======================================
  Files          27       27           
  Lines       26141    26141           
  Branches     1175     1175           
=======================================
  Hits        24398    24398           
  Misses       1713     1713           
  Partials       30       30           

Flag	Coverage Δ
c-tests	92.30% <ø> (ø)
lwt-tests	89.05% <ø> (ø)
python-c-tests	71.88% <100.00%> (ø)
python-tests	98.88% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
c/tskit/trees.c	95.23% <ø> (ø)
python/_tskitmodule.c	90.90% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9ce06f0...b43f0a6. Read the comment docs.

[jeromekelleher]

LGTM, thanks @benjeffery!