Adds span.kind:client for dalli

[zarirhamza]

What does this PR do?
Adds span.kind:client for dalli

Motivation
Unify span tags across tracers

[codecov-commenter]

Codecov Report

Merging #2619 (89786ea) into master (8022e0e) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2619      +/-   ##
==========================================
- Coverage   98.01%   98.01%   -0.01%     
==========================================
  Files        1148     1148              
  Lines       62423    62454      +31     
  Branches     2808     2808              
==========================================
+ Hits        61186    61215      +29     
- Misses       1237     1239       +2     

Impacted Files	Coverage Δ
...b/datadog/tracing/contrib/dalli/instrumentation.rb	100.00% <100.00%> (ø)
...dog/profiling/collectors/cpu_and_wall_time_spec.rb	97.58% <100.00%> (-0.31%)	⬇️
...filing/collectors/cpu_and_wall_time_worker_spec.rb	94.77% <100.00%> (+0.05%)	⬆️
spec/datadog/profiling/collectors/stack_spec.rb	97.29% <100.00%> (ø)
spec/datadog/profiling/spec_helper.rb	95.12% <100.00%> (+0.25%)	⬆️
spec/datadog/profiling/stack_recorder_spec.rb	100.00% <100.00%> (ø)
...adog/tracing/contrib/dalli/instrumentation_spec.rb	100.00% <100.00%> (ø)

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[GustavoCaso]

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