Use boost::optional and boost::none instead of smelly pointer (#24134)

* Remove bad pointer usage from CharacterCache

Use TrinityCore Option type instead which is intended for this purpose. (Wrapper around boost::option until C++17 bump is finalised)

* Unify codestyle regarding TC optional type

Based upon advice from @Shauren

(cherry picked from commit 76831f1f46)

src/server/game/Scripting/ScriptReloadMgr.cpp

@@ -278,7 +278,7 @@ Optional<std::shared_ptr<ScriptModule>>
                          path.generic_string().c_str());
         }
 
-        return boost::none;
+        return {};
     }
 
     // Use RAII to release the library on failure.
@@ -305,7 +305,7 @@ Optional<std::shared_ptr<ScriptModule>>
         TC_LOG_ERROR("scripts.hotswap", "Could not extract all required functions from the shared library \"%s\"!",
             path.generic_string().c_str());
 
-        return boost::none;
+        return {};
     }
 }