Fix detection and propagation of FSRs from input files

Instead of trying to open the input file (which fails when dealing with LFNs) we use, if available, the new incident introduced with gaudi/Gaudi!1456 (merged).

I also added a new incident to notify possible listeners that an FSR has been read from the input file.

Note: Needs Gaudi v36r13

/cc @cburr @egraveri

Kernel/FileSummaryRecord/include/LHCb/FileSummaryRecordIncident.h

+/*****************************************************************************\
+* (c) Copyright 2023 CERN for the benefit of the LHCb Collaboration           *
+*                                                                             *
+* This software is distributed under the terms of the GNU General Public      *
+* Licence version 3 (GPL Version 3), copied verbatim in the file "COPYING".   *
+*                                                                             *
+* In applying this licence, CERN does not waive the privileges and immunities *
+* granted to it by virtue of its status as an Intergovernmental Organization  *
+* or submit itself to any jurisdiction.                                       *
+\*****************************************************************************/
+#include <GaudiKernel/Incident.h>
+#include <nlohmann/json.hpp>
+
+namespace LHCb {
+  /// Simple incident to notify listeners that a new FSR has been read from an input file.
+  struct FileSummaryRecordIncident final : Incident {
+    static constexpr const char* Type = "FileSummaryRecordIncident";
+    FileSummaryRecordIncident( const std::string& source, const nlohmann::json& data )
+        : Incident{source, Type}, data{data} {}
+    ~FileSummaryRecordIncident() = default;
+    const nlohmann::json& data;
+  };
+} // namespace LHCb