Log the exception when a gRPC response frame is invalid

[thswlsqls]

Fixes #8625

Description

• OkHttpGrpcSender.handleResponse() caught the IOException from reading the 5-byte gRPC frame header but logged only a message, dropping the cause. The two sibling catch blocks in the same method already pass it ("Failed to read response body", e and "Failed to decompress response body", e).
• Diagnostics-only, no behavior change: the branch, the returned response, and the log message string are unchanged — the log record just gains its thrown field.
• A gRPC error response with grpc-status in the headers and an empty body reaches this branch via EOFException.
• Introduced by Response body bounds #8224 (b665652), which added this branch and the compliant sibling in the same commit.

Testing done

• No test added: nothing observable changes, and no existing test asserts this log record.
• ./gradlew :exporters:sender:okhttp:check — 42 tests passed.
• No apidiff or CHANGELOG entry: io.opentelemetry.exporter.sender.okhttp.internal is internal and the change is not user-facing.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.60%. Comparing base (b86f040) to head (70c6836).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8626   +/-   ##
=========================================
  Coverage     91.60%   91.60%           
  Complexity    10343    10343           
=========================================
  Files          1013     1013           
  Lines         27352    27352           
  Branches       3215     3215           
=========================================
  Hits          25057    25057           
  Misses         1567     1567           
  Partials        728      728           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.