Allow passing request_queuing option to Rack through Rails tracer

[KieranP]

Supporting this means I don't need to add and hacky overrides

[marcotc]

Thank you, @KieranP! 🙇

[codecov-commenter]

Codecov Report

Merging #2082 (398cdae) into master (0646d7d) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2082      +/-   ##
==========================================
- Coverage   97.49%   97.49%   -0.01%     
==========================================
  Files        1031     1031              
  Lines       53218    53218              
==========================================
- Hits        51884    51883       -1     
- Misses       1334     1335       +1     

Impacted Files	Coverage Δ
...og/tracing/contrib/rails/configuration/settings.rb	97.14% <100.00%> (+0.08%)	⬆️
lib/datadog/tracing/contrib/rails/framework.rb	100.00% <100.00%> (ø)
spec/datadog/profiling/ext/forking_spec.rb	99.39% <0.00%> (-0.61%)	⬇️
lib/datadog/core/diagnostics/environment_logger.rb	100.00% <0.00%> (ø)

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[ivoanjo]

👋 @KieranP this change has been released in v1.2.0.
Thank you so much for the cool contribution :)