Cranelift: Derive Copy for InstructionData (#5043)

* Cranelift: Derive `Copy` for `InstructionData`

And update `clone` calls to be copies.

* Add a test for `InstructionData`'s size

cranelift/codegen/src/ir/instructions.rs

@@ -755,6 +755,19 @@ mod tests {
     use super::*;
     use alloc::string::ToString;
 
+    #[test]
+    fn inst_data_is_copy() {
+        fn is_copy<T: Copy>() {}
+        is_copy::<InstructionData>();
+    }
+
+    #[test]
+    fn inst_data_size() {
+        // The size of `InstructionData` is performance sensitive, so make sure
+        // we don't regress it unintentionally.
+        assert_eq!(std::mem::size_of::<InstructionData>(), 16);
+    }
+
     #[test]
     fn opcodes() {
         use core::mem;