Add unit tests for MarshalerInputStream

[Vicky677]

Description

Adds comprehensive unit test coverage for io.opentelemetry.exporter.internal.grpc.MarshalerInputStream in opentelemetry-exporter-common.

Test scenarios covered:

• available():
  • Checking available bytes when backed by a MessageWriter.
  • Checking available bytes when backed by a partial ByteArrayInputStream.
  • Returning 0 after the stream has been fully drained.
• drainTo(OutputStream):
  • Draining directly from a MessageWriter.
  • Draining from an already existing partial stream.
  • Returning 0 written bytes when called on an already drained stream.
• read() (single byte):
  • Reading single bytes sequentially until EOF (-1) from a MessageWriter.
  • Reading single bytes from a partial stream.
  • Returning -1 on already drained stream.
• read(byte[], int, int) (bulk read):
  • Reading bulk byte array from a MessageWriter and verifying EOF on subsequent read.
  • Handling 0-length messages properly.
  • Reading bulk bytes from a partial stream.
  • Returning -1 on already drained stream.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Vicky677 / name: Abhishek.Ghosh11 (38251b8)

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Waiting on reviewers · refreshed 2026-09-12 10:50 UTC

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.37%. Comparing base (1270b3d) to head (42d5362).
⚠️ Report is 20 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8784      +/-   ##
============================================
+ Coverage     91.30%   91.37%   +0.07%     
- Complexity    10506    10537      +31     
============================================
  Files          1007     1008       +1     
  Lines         28373    28465      +92     
  Branches       3586     3617      +31     
============================================
+ Hits          25907    26011     +104     
+ Misses         1673     1658      -15     
- Partials        793      796       +3     

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