[chore] Fix bug in exporter.Request.MergeSplit()

[sfc-gh-sili]

Description

This PR fixes logsRequest, tracesRequest and metricsRequest to NOT modify the input if MergeSplit() returns an error. Copy-pasted the doc string of MergeSplit() for references:

// MergeSplit is a function that merge and/or splits this request with another one into multiple requests based on the
// configured limit provided in MaxSizeConfig.
// All the returned requests MUST have a number of items that does not exceed the maximum number of items.
// Size of the last returned request MUST be less or equal than the size of any other returned request.
// The original request MUST not be mutated if error is returned after mutation or if the exporter is
// marked as not mutable. The length of the returned slice MUST not be 0.
// Experimental: This API is at the early stage of development and may change without backward compatibility
// until #8122 is resolved.
MergeSplit(context.Context, exporterbatcher.MaxSizeConfig, Request) ([]Request, error)

Link to tracking issue

Fixes #

Testing

Added TestMergeSplit{Logs, Traces, Metrics}InputNotModifiedIfErrorReturned

Documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.65%. Comparing base (b4ae0ba) to head (08a3a33).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12009      +/-   ##
==========================================
+ Coverage   91.62%   91.65%   +0.02%     
==========================================
  Files         447      447              
  Lines       23737    23746       +9     
==========================================
+ Hits        21749    21764      +15     
+ Misses       1613     1609       -4     
+ Partials      375      373       -2     

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