Fix clippy warnings across workspace

- io.rs: factor the pending-RPC-replies map into a PendingReplies
  type alias (type_complexity)
- lua_env.rs: drop a redundant i64->i64 cast and an unneeded borrow
  before create_string (unnecessary_cast, needless_borrows_for_generic_args)
- state_engine.rs: iterate watches.values() instead of discarding the
  key from watches.iter() (for_kv_map)
- module_host_sandbox.rs: collapse nested if into a single condition
  (collapsible_if)

(cherry picked from commit 49063cb98ddfeae35d842a6cf439123cfda763d9)

bread-module-host/src/io.rs

@@ -33,6 +33,10 @@ pub enum IoCommand {
     },
 }
 
+/// In-flight RPC calls awaiting a response, keyed by request id: each entry
+/// is the reply channel for the call that's blocked waiting on it.
+type PendingReplies = Arc<Mutex<HashMap<String, mpsc::Sender<Result<Value, String>>>>>;
+
 /// Something the IO thread has for the Lua-driving thread: either an
 /// unsolicited push (a subscribed event fired, a timer fired) or "the
 /// connection is gone" (breadd exited, socket closed, etc).
@@ -148,8 +152,7 @@ pub fn run(
         // Lua-side call is blocked waiting for them; a dedicated thread
         // bridges the synchronous `cmd_rx` (fed from the Lua thread) onto an
         // async channel this task can select on.
-        let pending: Arc<Mutex<HashMap<String, mpsc::Sender<Result<Value, String>>>>> =
-            Arc::new(Mutex::new(HashMap::new()));
+        let pending: PendingReplies = Arc::new(Mutex::new(HashMap::new()));
 
         let (async_cmd_tx, mut async_cmd_rx) = tokio::sync::mpsc::unbounded_channel::<IoCommand>();
         std::thread::spawn(move || {

bread-module-host/src/lua_env.rs

@@ -93,7 +93,7 @@ fn json_to_lua<'lua>(lua: &'lua Lua, value: &JsonValue) -> mlua::Result<LuaValue
         JsonValue::Bool(b) => LuaValue::Boolean(*b),
         JsonValue::Number(n) => {
             if let Some(i) = n.as_i64() {
-                LuaValue::Integer(i as i64)
+                LuaValue::Integer(i)
             } else {
                 LuaValue::Number(n.as_f64().unwrap_or(0.0))
             }
@@ -243,7 +243,7 @@ impl ModuleHostLua {
         let decode_fn = lua.create_function(|lua, s: String| {
             match serde_json::from_str::<JsonValue>(&s) {
                 Ok(v) => Ok((json_to_lua(lua, &v)?, LuaValue::Nil)),
-                Err(e) => Ok((LuaValue::Nil, LuaValue::String(lua.create_string(&e.to_string())?))),
+                Err(e) => Ok((LuaValue::Nil, LuaValue::String(lua.create_string(e.to_string())?))),
             }
         })?;
         json_tbl.set("decode", decode_fn)?;