more child-process

[pfgithub]

• test-cluster-worker-kill-signal was flaky before this PR. no change.
• next-build was flaky before this PR. no change

Fixes a memory leak when spawning multiple child processes using IPC

[robobun]

^{Updated 11:07 PM PT - May 6th, 2025}

❌ @pfgithub, your commit b09dfe6 has 1 failures in Build #16226:

• test/js/bun/s3/s3.test.ts - timeout on 🍎 13 aarch64
• test/js/bun/s3/s3.test.ts - timeout on 🍎 14 aarch64
• test/js/bun/s3/s3.test.ts - timeout on 🍎 14 x64

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🧪   To try this PR locally:

bunx bun-pr 18688

That installs a local version of the PR into your bun-18688 executable, so you can run:

bun-18688 --bun