feat: implement & test open_at

host/src/component.rs

@@ -298,7 +298,7 @@ impl WasmComponentInstance {
         let component = component.hydrate(&engine)?;
 
         // resource/mem limiter
-        let mut limiter = Limiter::new(permissions.resource_limits.clone(), memory_pool);
+        let limiter = Limiter::new(permissions.resource_limits.clone(), memory_pool);
 
         // Create in-memory VFS
         let vfs_state = VfsState::new(permissions.vfs.clone(), limiter.clone());

host/src/limiter.rs

@@ -78,7 +78,7 @@ impl Limiter {
     }
 
     /// Grow memory usage.
-    pub(crate) fn grow(&mut self, bytes: usize) -> Result<(), GrowthError> {
+    pub(crate) fn grow(&self, bytes: usize) -> Result<(), GrowthError> {
         let mut self_guard = self
             .memory_reservation
             .lock()