fix(data-structures): ensure size consistency in RedBlackTree.from

[jiangshengdev]

Previously, when cloning an existing RedBlackTree using the static from method, the new tree’s #size field was not updated, leading to a mismatch between the reported size and the actual number of nodes. This commit addresses the issue by directly assigning the original tree’s #size to the new instance after copying all nodes.

Additional tests have been added to verify that size remains accurate and consistent following the cloning process.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.33%. Comparing base (c40f593) to head (e4501cf).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6307   +/-   ##
=======================================
  Coverage   96.33%   96.33%           
=======================================
  Files         547      547           
  Lines       41667    41671    +4     
  Branches     6314     6314           
=======================================
+ Hits        40140    40145    +5     
  Misses       1484     1484           
+ Partials       43       42    -1     

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[kt3k]

LGTM. Thanks!