refactor: fix clang-tidy warnings

Enable and fix bugprone-misplaced-widening-cast warning.

Fix some modernize-macro-to-enum and readability-else-after-return
warnings, but don't enable them. While the warnings can be useful, they
are in general too noisy to enable.

src/nvim/lua/converter.c

@@ -906,9 +906,8 @@ Float nlua_pop_Float(lua_State *lstate, Error *err)
   lua_pop(lstate, 1);
   if (table_props.type != kObjectTypeFloat) {
     return 0;
-  } else {
-    return (Float)table_props.val;
   }
+  return (Float)table_props.val;
 }
 
 /// Convert lua table to array without determining whether it is array