Decouple test reporter IO from test execution

[alexcrocha]

Motivation

This PR solves the LspReporter's IO bottleneck (as identified in #3843) by decoupling socket writes from test execution. When the reporter is active, every test result blocks the test thread until the OS completes a socket write. For suites with many fast tests, this IO overhead becomes the bottleneck and can degrade test runtime.

Implementation

send_message now pushes to a Thread::Queue instead of writing to the socket directly. A background writer thread pops messages from the queue and writes them to the socket, so the test thread never blocks on IO.

Shutdown uses Queue#close to signal the writer thread that no more messages will be enqueued, allowing it to exit after processing the remaining ones.

Automated Tests

The existing tests should continue to pass with this change as the external behaviour remains the same.

[alexcrocha]

• Decouple test reporter IO from test execution #3962 👈 (View in Graphite)
• main

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