[CODE HEALTH] Fix clang-tidy cppcoreguidelines-init-variables warnings

[dbarker]

Fixes # (issue)

Changes

• fix clang-tidy cppcoreguidelines-init-variables warnings

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.06%. Comparing base (355bf9b) to head (e31ce24).

Files with missing lines	Patch %	Lines
...ude/opentelemetry/sdk/metrics/view/view_registry.h	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3919      +/-   ##
==========================================
- Coverage   90.07%   90.06%   -0.00%     
==========================================
  Files         226      226              
  Lines        7217     7223       +6     
==========================================
+ Hits         6500     6505       +5     
- Misses        717      718       +1     

Files with missing lines	Coverage Δ
api/include/opentelemetry/baggage/baggage.h	98.28% <100.00%> (+0.02%)	⬆️
...entelemetry/trace/propagation/http_trace_context.h	92.86% <100.00%> (+0.22%)	⬆️
...i/include/opentelemetry/trace/propagation/jaeger.h	97.83% <100.00%> (+0.05%)	⬆️
api/include/opentelemetry/trace/trace_state.h	97.62% <100.00%> (+0.03%)	⬆️
...ude/opentelemetry/sdk/metrics/view/view_registry.h	81.36% <0.00%> (-1.40%)	⬇️

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[marcalff]

LGTM, thanks for the cleanup.