Add CONCURRENCY operator support to Query Specification

[jharley]

Adds support for the CONCURRENCY operator.

Resolves #108

[codecov-commenter]

Codecov Report

Merging #112 (689dc7b) into main (06686a2) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #112      +/-   ##
==========================================
+ Coverage   85.62%   85.65%   +0.02%     
==========================================
  Files          25       25              
  Lines        1795     1798       +3     
==========================================
+ Hits         1537     1540       +3     
  Misses        204      204              
  Partials       54       54              

Impacted Files	Coverage Δ
client/query_spec.go	92.98% <100.00%> (+0.38%)	⬆️
honeycombio/data_source_query_specification.go	95.14% <100.00%> (ø)

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