Run Bazel tests in parallel in CI

[wasphin]

What problem does this PR solve?

Issue Number: resolve

Problem Summary:

The Clang Bazel unit-test job uses streamed test output for the full test suite. Bazel runs streamed tests locally and serially, which prevents independent test targets from running in parallel and makes this job a CI critical path.

Some tests also rely on fixed ports, TCP response packet boundaries, or Bazel's default timeout, which makes them unreliable when independent targets run concurrently.

What is changed and the side effects?

Changed:

• Change the Clang Bazel unit-test output mode from streamed to errors so Bazel can schedule independent test targets in parallel.
• Use ephemeral ports in the interceptor and HTTP expect tests.
• Preserve HTTP responses already buffered from the same connection between reads.
• Declare the protobuf JSON test as a large Bazel test so its timeout reflects its existing runtime under CI contention.
• Preserve failure diagnostics: failed test output is printed and complete test logs remain available under bazel-testlogs.

Side effects:

• Performance effects: Reduces the wall-clock duration of the Clang Bazel unit-test job by enabling normal Bazel test parallelism.

• Breaking backward compatibility: No. The production library is unchanged; this updates CI scheduling and test robustness.

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[wwbmmm]

LGTM