ZJIT: Investigate high RSS usage on protoboeuf

https://rubybench.github.io/#other

<img width="1353" height="973" alt="Image" src="https://github.com/user-attachments/assets/41f2fe05-f79f-4a26-b97d-e12d50ce1f51" />

`protoboeuf` benchmark shows a high memory usage with ZJIT enabled. We need to investigate why.