fix: avoid using C-style pointers to prevent potential memory leaks

[SYaoJun]

Reason for this PR

current Status missing copy assignment operator, which may cause memory leak.
modern cpp guidelines suggent using smart pointer instead of C-type pointer.

In this PR, it uses std::unique_ptr<State> state_; to replace orignal State* state_;

BTW, This memory leak was detected by .clang-tidy.

#898

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[Thespica]

cpp faild to buil

pleas fix that.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.58%. Comparing base (b21da29) to head (3a25e8f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #913      +/-   ##
============================================
- Coverage     80.60%   80.58%   -0.02%     
  Complexity      615      615              
============================================
  Files            94       94              
  Lines         10709    10698      -11     
  Branches       1055     1055              
============================================
- Hits           8632     8621      -11     
  Misses         1837     1837              
  Partials        240      240              

Flag	Coverage Δ
cpp	70.84% <100.00%> (-0.07%)	⬇️

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