Ensure that Datadog::Tracing::TraceSegment can be reported correctly when they are dropped

[DougEdey]

What does this PR do?

This proposes a fix for #2334

TraceSegment doesn't respond to map but the spans inside it do, so it should provide usable debug information going forward.

I'm not confident that the test is the best it can be, I'm just focused on the issue I've encountered, I had to change the logger statement to actually render the log line to ensure it works appropriately.

Motivation

I found the bug

Additional Notes

How to test the change?

[codecov-commenter]

Codecov Report

Merging #2335 (ecbac58) into master (0c66c3b) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2335      +/-   ##
==========================================
- Coverage   98.29%   98.29%   -0.01%     
==========================================
  Files        1092     1092              
  Lines       58041    58045       +4     
==========================================
+ Hits        57054    57056       +2     
- Misses        987      989       +2     

Impacted Files	Coverage Δ
spec/ddtrace/transport/http/builder_spec.rb	100.00% <ø> (ø)
lib/ddtrace/transport/traces.rb	97.82% <100.00%> (ø)
spec/datadog/core/configuration_spec.rb	100.00% <100.00%> (ø)
spec/datadog/core_spec.rb	100.00% <100.00%> (ø)
spec/ddtrace/transport/traces_spec.rb	97.93% <100.00%> (+0.04%)	⬆️
...adog/tracing/contrib/sidekiq/client_tracer_spec.rb	97.91% <0.00%> (-2.09%)	⬇️
...adog/tracing/contrib/sidekiq/server_tracer_spec.rb	99.16% <0.00%> (-0.84%)	⬇️

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[marcotc]

Thank you so much, @DougEdey!

I've made a few changes, but the scenario your reported is indeed problematic. 🙇

[DougEdey]

Thanks @marcotc , I'm glad to see this fixed