Probably reduce memory usage of JSON IPC

[Jarred-Sumner]

What does this PR do?

Previously, we often cloned JSON strings an extra time over IPC.

Before merging, need to verify this does in fact reduce memory usage because currently this is just an educated guess

How did you verify your code works?

Added a test that roundtrip encodes & decodes latin1, ascii and utf-16 for IPC

[robobun]

^{Updated 7:06 PM PT - Jan 11th, 2025}

✅ @Jarred-Sumner, your commit 534eeb8 has passed in #9464! 🎉

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🧪   try this PR locally:

bunx bun-pr 16346