Improvement tskit treeseq from text mutations

[lukashuebner]

Fixes #2729

[codecov]

Codecov Report

Merging #2734 (5437546) into main (72a7add) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2734   +/-   ##
=======================================
  Coverage   94.08%   94.08%           
=======================================
  Files          29       29           
  Lines       28516    28516           
  Branches     1609     1609           
=======================================
  Hits        26828    26828           
  Misses       1653     1653           
  Partials       35       35           

Flag	Coverage Δ
c-tests	92.36% <ø> (ø)
lwt-tests	89.05% <ø> (ø)
python-c-tests	70.89% <ø> (ø)
python-tests	99.05% <ø> (ø)

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[jeromekelleher]

Thanks for this @lukashuebner - I think @petrelharp has done basically the same thing in #2730. See the discussion over there for why we're a bit nervous about always computing the parents like this.

[petrelharp]

Yes, thanks very much!