Return OutOfMemory from alloc_dynamic_table_elements on failure

This is more correct and also `ensure!` will attempt to allocate, which trips up
the OOM test framework.

Author: fitzgen

crates/wasmtime/src/runtime/vm/table.rs

@@ -314,7 +314,9 @@ unsafe fn alloc_dynamic_table_elements<T>(len: usize) -> Result<Vec<Option<T>>>
     let layout = Layout::from_size_align(size, align)?;
 
     let ptr = unsafe { alloc::alloc::alloc_zeroed(layout) };
-    ensure!(!ptr.is_null(), "failed to allocate memory for table");
+    if ptr.is_null() {
+        return Err(OutOfMemory::new(size).into());
+    }
 
     let elems = unsafe { Vec::<Option<T>>::from_raw_parts(ptr.cast(), len, len) };
     debug_assert!(elems.iter().all(|e| e.is_none()));