refactor: some restructuring

- move structs inside `sr_tools.rs` into individual file
- implement in-game equip handler (relic & lightcone)

common/src/structs/mod.rs

@@ -0,0 +1,47 @@
+use proto::ItemType;
+
+pub mod avatar;
+pub mod battle;
+pub mod lightcone;
+pub mod monster;
+pub mod persistent;
+pub mod relic;
+pub mod scene;
+
+pub use avatar::*;
+pub use battle::*;
+pub use lightcone::*;
+pub use monster::*;
+pub use persistent::*;
+pub use scene::*;
+
+pub fn get_item_unique_id(internal_uid: u32, item_type: ItemType) -> u32 {
+    if item_type == ItemType::ItemEquipment {
+        2000 + internal_uid // 2000.3500
+    } else {
+        1 + internal_uid // 1..2000
+    }
+}
+
+#[macro_export]
+macro_rules! impl_from {
+    ($from:ty, $to:ty, |$param:ident| $body:block) => {
+        impl From<$from> for $to {
+            fn from($param: $from) -> Self {
+                $body
+            }
+        }
+
+        impl From<&$from> for $to {
+            fn from($param: &$from) -> Self {
+                $body
+            }
+        }
+
+        impl From<&mut $from> for $to {
+            fn from($param: &mut $from) -> Self {
+                $body
+            }
+        }
+    };
+}