Use fixed-width C int for Vulkan FD exports

[antono3]

Summary

Use i32 for the Vulkan registry's C int fields and parameters. In particular, vkGetMemoryFdKHR, vkGetSemaphoreFdKHR, and vkGetFenceFdKHR write to 32-bit C int* outputs. V3's 64-bit int leaves the upper half of an initialized FD unchanged, so callers can receive a negative value even when Vulkan reports success.

This source reflects the generator mapping in antono2/v_vulkan_bindings#16. The generated C.int placeholder is no longer needed.

Verification

• V 0.5.2: all 5 ergonomic tests pass; current particle example compiles and completes zero-copy memory and semaphore smoke tests with the matching caller changes.
• Current V3 with local compiler fixes from v3: use emitted fixed-array names in function pointers vlang/v#28902 and v3: pass dynamic array data pointers without autoref vlang/v#28903: particle example compiles and completes the same zero-copy smoke tests.
• v fmt -verify vulkan.v and git diff --check pass.

The particle call-site update is a separate antono2/opencl PR.