Refactor SetWriter function to allow resetting output to os.Stdout

[trheyi]

• Updated SetWriter to accept nil as an argument to reset the output target to os.Stdout.
• Modified unit tests to utilize a buffered writer for capturing output during tests, ensuring consistent logging behavior.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.30%. Comparing base (52c719f) to head (a82cdcf).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #28      +/-   ##
==========================================
- Coverage   89.93%   89.30%   -0.64%     
==========================================
  Files           9        9              
  Lines        1093      972     -121     
==========================================
- Hits          983      868     -115     
+ Misses        101       95       -6     
  Partials        9        9              

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