[chore] Add tests for network code propagation with consumererror

[evan-bradley]

This adds some E2E tests that show how network codes propagate from the OTLP(/HTTP) exporter to the OTLP receiver (both serving over HTTP and gRPC). The goal is that as we add the new consumererror.Error type and any related types to the pipeline, we can use these tests to understand the net effect of the errors.

Most of the tests won't require changes after we add the new error type, but note the comment in TestHTTPToHTTP that shows where the error type will add functionality.

These tests don't cover a few things right now:

• Any transformation of the errors as they travel back up the pipeline by internal parts of the the pipeline graph (fanouts, obsreporter, etc.). These could impact what the OTLP receiver returns, so we may want to test them later as we touch those components. We may want these direct tests regardless since these components have a contract with each other that likely should exist outside our service implementation.
• Retry handling. This hasn't been fully added to the errors yet, so I'll wait until that's closer to add tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.45%. Comparing base (f87c5ba) to head (a3e5468).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13424      +/-   ##
==========================================
+ Coverage   91.41%   91.45%   +0.04%     
==========================================
  Files         533      533              
  Lines       29564    29564              
==========================================
+ Hits        27026    27038      +12     
+ Misses       2004     1995       -9     
+ Partials      534      531       -3     

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