Function jit_v2_alloc_struct 

#[unsafe(no_mangle)]
pub extern "C" fn jit_v2_alloc_struct(size: u32, kind: u16) -> *mut u8

Allocate a v2 struct of the given total size (including header). Initializes the HeapHeader with refcount=1 and the given kind. Returns a pointer to the start of the struct (i.e., to the HeapHeader).