Remove unnecessary serde_json dependency from logs feature

[Copilot]

The logs feature in opentelemetry-sdk was incorrectly including serde_json as a dependency, which is not needed for basic logs functionality. This was causing unnecessary bloat for users who only want logging capabilities without JSON serialization.

Changes Made

1. Removed serde_json from logs feature: Updated the feature definition in Cargo.toml from:

   logs = ["opentelemetry/logs", "opentelemetry/trace", "serde_json"]

   to:

   logs = ["opentelemetry/logs", "opentelemetry/trace"]

2. Fixed deprecated API usage in tests: Updated test code to use current APIs:

   • TraceId::from_u128(13) → TraceId::from(13u128)
   • SpanId::from_u64(14) → SpanId::from(14u64)

Verification

• ✅ Logs feature compiles and works correctly without serde_json
• ✅ jaeger_remote_sampler feature continues to work with its own explicit serde_json dependency
• ✅ All existing functionality remains intact
• ✅ Created and tested minimal example confirming logs work without JSON dependencies

The serde_json dependency is only used by the jaeger_remote_sampler feature for parsing remote sampling configuration, and that feature already has its own explicit dependency on serde_json. This change reduces the dependency footprint for users who only need logging capabilities.

Fixes #3104.

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[linux-foundation-easycla]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.1%. Comparing base (0462369) to head (7215d45).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3106   +/-   ##
=====================================
  Coverage   80.1%   80.1%           
=====================================
  Files        126     126           
  Lines      21957   21957           
=====================================
  Hits       17603   17603           
  Misses      4354    4354           

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