Avoid struct name repetitions.

lib/runtime/src/instance.rs

@@ -843,7 +843,7 @@ impl InstanceHandle {
 impl Clone for InstanceHandle {
     fn clone(&self) -> Self {
         unsafe { &mut *(self.instance as *mut Instance) }.refcount += 1;
-        InstanceHandle {
+        Self {
             instance: self.instance,
         }
     }

lib/runtime/src/vmcontext.rs

@@ -409,7 +409,7 @@ mod test_vmshared_signature_index {
 impl VMSharedSignatureIndex {
     /// Create a new `VMSharedSignatureIndex`.
     pub fn new(value: u32) -> Self {
-        VMSharedSignatureIndex(value)
+        Self(value)
     }
 }