Improve MultiSplit child reconciliation without unnecessary rerenders

[philippjfr]

• Skip insert/append when object updates are pure removals
• Avoid rerendering children that remain in the same position
• Rerender components that are re-inserted in the DOM, ensuring correctness

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.12%. Comparing base (77e6832) to head (3d2ba33).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #25   +/-   ##
=======================================
  Coverage   87.12%   87.12%           
=======================================
  Files           3        3           
  Lines         101      101           
=======================================
  Hits           88       88           
  Misses         13       13           

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