Refactor initialize_vmcontext.

This was originally written to support sourcing the table and memory
definitions differently for the pooling allocator.

However, both allocators do the exact same thing, so the closure arguments are
no longer necessary.

Additionally, this cleans up the code a bit to pass in the allocation request
rather than having individual parameters.

crates/runtime/src/instance/allocator/pooling.rs

@@ -430,7 +430,7 @@ impl InstancePool {
     fn allocate(
         &self,
         strategy: PoolingAllocationStrategy,
-        req: InstanceAllocationRequest,
+        mut req: InstanceAllocationRequest,
     ) -> Result<InstanceHandle, InstantiationError> {
         let index = {
             let mut free_list = self.free_list.lock().unwrap();
@@ -441,17 +441,19 @@ impl InstancePool {
             free_list.swap_remove(free_index)
         };
 
+        let host_state = std::mem::replace(&mut req.host_state, Box::new(()));
+
         unsafe {
             debug_assert!(index < self.max_instances);
             let instance =
                 &mut *(self.mapping.as_mut_ptr().add(index * self.instance_size) as *mut Instance);
 
-            instance.module = req.module;
+            instance.module = req.module.clone();
             instance.offsets = VMOffsets::new(
                 std::mem::size_of::<*const u8>() as u8,
                 instance.module.as_ref(),
             );
-            instance.host_state = req.host_state;
+            instance.host_state = host_state;
 
             Self::set_instance_memories(
                 instance,
@@ -460,20 +462,7 @@ impl InstancePool {
             )?;
             Self::set_instance_tables(instance, self.tables.get(index), self.tables.max_elements)?;
 
-            initialize_vmcontext(
-                instance,
-                req.imports.functions,
-                req.imports.tables,
-                req.imports.memories,
-                req.imports.globals,
-                req.finished_functions,
-                req.lookup_shared_signature,
-                req.interrupts,
-                req.externref_activations_table,
-                req.stack_map_registry,
-                &|index| instance.memories[index].vmmemory(),
-                &|index| instance.tables[index].vmtable(),
-            );
+            initialize_vmcontext(instance, req);
 
             Ok(InstanceHandle::new(instance as _))
         }
@@ -517,6 +506,9 @@ impl InstancePool {
                     decommit(base, size);
                 }
             }
+
+            // Drop the host state
+            (*handle.instance).host_state = Box::new(());
         }
 
         {