Removing package integration from coverage reports

[rbroggi]

Which problem is this PR solving?

• Make coverage reports more accurate

Short description of the changes

• Package integration is a test-only package for integration tests. The files integration.go and trace_compare.go bundle test-utilities and therefore should not be considered for coverage reports (quite in the same way *_test.go files are not eligible too).

[codecov]

Codecov Report

Merging #3357 (bdbeea4) into master (8b7772e) will increase coverage by 0.41%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3357      +/-   ##
==========================================
+ Coverage   96.01%   96.43%   +0.41%     
==========================================
  Files         261      259       -2     
  Lines       15464    15166     -298     
==========================================
- Hits        14848    14625     -223     
+ Misses        523      456      -67     
+ Partials       93       85       -8     

Impacted Files	Coverage Δ
cmd/collector/app/server/zipkin.go	68.29% <0.00%> (-2.44%)	⬇️
cmd/query/app/server.go	94.11% <0.00%> (-1.48%)	⬇️
plugin/storage/badger/spanstore/reader.go	95.50% <0.00%> (-0.71%)	⬇️
plugin/storage/integration/integration_test.go
plugin/storage/integration/trace_compare_test.go

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