Shared/Logs: Improve log performances

Improve Log::ShouldLog() performances by saving the lowest log level across all loggers and discarding any log with lower level than that.

src/server/shared/Logging/Log.cpp

@@ -199,6 +199,9 @@ void Log::CreateLoggerFromConfig(std::string const& appenderName)
         return;
     }
 
+    if (level < lowestLogLevel)
+        lowestLogLevel = level;
+
     logger.Create(name, level);
     //fprintf(stdout, "Log::CreateLoggerFromConfig: Created Logger %s, Level %u\n", name.c_str(), level);
 
@@ -394,6 +397,7 @@ void Log::LoadFromConfig()
 {
     Close();
 
+    lowestLogLevel = LOG_LEVEL_FATAL;
     AppenderId = 0;
     m_logsDir = sConfigMgr->GetStringDefault("LogsDir", "");
     if (!m_logsDir.empty())