Fix IWYU Clang22 warnings

[marcalff]

Fixes # (issue)

Changes

Please provide a brief description of the changes here.

• Fix new IWYU warnings detected after the upgrade to iwyu clang 22

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.99%. Comparing base (16b1369) to head (54addfa).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4083      +/-   ##
==========================================
- Coverage   82.01%   81.99%   -0.01%     
==========================================
  Files         385      385              
  Lines       16023    16023              
==========================================
- Hits        13139    13137       -2     
- Misses       2884     2886       +2     

Files with missing lines	Coverage Δ
api/include/opentelemetry/nostd/variant.h	66.67% <ø> (ø)
...y/exporters/elasticsearch/es_log_record_exporter.h	0.00% <ø> (ø)
...emetry/exporters/elasticsearch/es_log_recordable.h	0.00% <ø> (ø)
...orters/elasticsearch/src/es_log_record_exporter.cc	0.00% <ø> (ø)
exporters/elasticsearch/src/es_log_recordable.cc	65.39% <ø> (ø)
exporters/ostream/src/metric_exporter.cc	91.10% <ø> (ø)
...opentelemetry/exporters/otlp/otlp_log_recordable.h	100.00% <ø> (ø)
exporters/otlp/src/otlp_file_client.cc	70.38% <ø> (ø)
exporters/otlp/src/otlp_file_metric_exporter.cc	90.25% <ø> (ø)
exporters/otlp/src/otlp_grpc_client.cc	71.53% <ø> (ø)
... and 39 more

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