Revert "Remove unused variables" (#5667)

This reverts commit f070b22355.

BTCPayServer.Common/Logging/ConsoleLogger.cs

@@ -174,6 +174,7 @@ namespace BTCPayServer.Logging
             logLevelColors = GetLogLevelConsoleColors(logLevel);
             logLevelString = GetLogLevelString(logLevel);
             // category and event id
+            var lenBefore = logBuilder.ToString().Length;
             logBuilder.Append(_loglevelPadding);
             logBuilder.Append(logName);
             logBuilder.Append(": ");