[CODE HEALTH] Move logger_sdk_test classes into anonymous namespace

[thc1006]

Summary

Wraps the 6 file-scope class and struct declarations in
sdk/test/logs/logger_sdk_test.cc within an anonymous namespace,
clearing the corresponding misc-use-internal-linkage warnings.

This is the 5th PR of the misc-use-internal-linkage campaign (#4115,
#4116, #4121, #4122 already merged) and the first with an asymmetric
ratchet drop because 2 of the 6 wrapped classes are inside an
#if OPENTELEMETRY_ABI_VERSION_NO >= 2 gate.

Changes

• sdk/test/logs/logger_sdk_test.cc: insert namespace { after the
  first TEST(LoggerSDK, LogToNullProcessor) (ends at line 117) and
  } // namespace after the final #endif of the file-trailing
  #if OPENTELEMETRY_ABI_VERSION_NO < 2 block. Wrap covers:
  • MockLogRecordable (line 119, always-on)
  • MockProcessor (line 241, always-on)
  • EnabledProcessorCallState struct (line 276, abiv2-only)
  • EnablementAwareProcessor (line 286, abiv2-only)
  • CustomLogConfiguratorTestData (line 668, always-on)
  • CustomLoggerConfiguratorTestFixture TEST_P fixture (line 747,
    always-on)
• The pre-existing anonymous namespace at lines 65-99 (wrapping two
  abiv2 helper functions inside an existing #if abiv2 gate) is left
  in place.
• .github/workflows/clang-tidy.yaml: abiv1 356 -> 352 (-4),
  abiv2 362 -> 356 (-6).
• CHANGELOG.md: one bullet under [Unreleased].

Why the ratchet drop is asymmetric

#if OPENTELEMETRY_ABI_VERSION_NO >= 2 at lines 275-338 contains
EnabledProcessorCallState and EnablementAwareProcessor. In abiv1
builds the preprocessor strips these out, so clang-tidy never sees
them and they are not counted in the abiv1 baseline of 356. In abiv2
builds they are visible and contribute 2 of the 362 total warnings.

After this PR clears all 6 sites, both ratchets drop by the count
visible in that build (abiv1: -4, abiv2: -6), and 2 of the abiv2-only
classes also stop counting against the abiv2 baseline. Net new limits:
abiv1 352, abiv2 356.

This is mechanically the same wrap as #4115 / #4116 / #4121 / #4122;
the only novelty is that this is the first wrapped file containing an
ABI-gated class.

Test plan

• Local abiv1 build of logger_sdk_test: 59/59 ninja steps
  (WITH_OTLP_HTTP=OFF -DWITH_OTLP_GRPC=OFF)
• Local abiv1 run: 9/9 tests pass
• Local abiv2 build of logger_sdk_test:
  -DWITH_ABI_VERSION_2=ON -DWITH_ABI_VERSION_1=OFF, 59/59 steps
• Local abiv2 run: 15/15 tests pass (extra 6 tests are
  abiv2-only, exercising EnabledProcessorCallState and
  EnablementAwareProcessor)
• clang-format --dry-run --Werror clean on the modified file
• DCO signed off

Part of #2053

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.94%. Comparing base (d2f09f1) to head (1bb67df).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4124      +/-   ##
==========================================
- Coverage   81.95%   81.94%   -0.01%     
==========================================
  Files         385      385              
  Lines       16067    16067              
==========================================
- Hits        13166    13164       -2     
- Misses       2901     2903       +2     

see 1 file with indirect coverage changes

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