[ENH] Even faster unsupervised forests and trees

[adam2392]

Fixes #13

Changes proposed in this pull request:

• Removes the extra for loops in update that have to recompute the statistics.

• All statistics are computed and stored in a hash map during init_feature_vec

• Re-assign and compute statistics w/o a for-loop during update.

• Just inlines functions

• updates wrt scikit-learn main

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[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (fc48cef) 86.73% compared to head (ba2a3bf) 86.73%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #117   +/-   ##
=======================================
  Coverage   86.73%   86.73%           
=======================================
  Files          26       26           
  Lines        2111     2111           
=======================================
  Hits         1831     1831           
  Misses        280      280           

Files Changed	Coverage Δ
sktree/tests/test_honest_forest.py	100.00% <ø> (ø)
sktree/tree/_classes.py	75.00% <100.00%> (ø)
sktree/tree/tests/test_unsupervised_tree.py	100.00% <100.00%> (ø)

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