Revert "change asset id to string"

This reverts commit 8430929.

Author: darunrs

lazer/sdk/rust/protocol/src/lib.rs

@@ -35,9 +35,9 @@ pub use crate::{
 };
 
 #[derive(
-    Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize, From, Into,
+    Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize, From, Into,
 )]
-pub struct AssetId(pub String);
+pub struct AssetId(pub u32);
 
 #[derive(
     Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize, From, Into,