test: improve test coverage for pkg/util/log

[everfid-ever]

What this PR does:
Add additional unit tests for the pkg/util/log package to improve test coverage and validate error-handling scenarios.

Which issue(s) this PR fixes:
Fixes #961

Special notes for your reviewer:

• Added tests for zap initialization failures, fatal log behavior, and concurrent writes.
• Current coverage increased from 0% - 73.6%.
• No logic changes to production code.

Does this PR introduce a user-facing change?:

NONE

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 46.59%. Comparing base (4420143) to head (dc1cbc8).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #964      +/-   ##
==========================================
+ Coverage   46.33%   46.59%   +0.25%     
==========================================
  Files         195      196       +1     
  Lines       11887    12006     +119     
==========================================
+ Hits         5508     5594      +86     
- Misses       5943     5972      +29     
- Partials      436      440       +4     

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[slievrly]

LGTM