refactor: some restructuring

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

gameserver/src/net/handlers/chat.rs

@@ -1,4 +1,4 @@
-use common::sr_tools::MultiPathAvatar;
+use common::structs::MultiPathAvatar;
 
 use crate::{net::PlayerSession, util::cur_timestamp_ms};