Add gsf and idperf chains to LS2, updated references

This is the first step of cleaning up e/γ LS2 menu. Several GSF chains have been added to study their performance and evaluate where they can be used in the physics menu. Additional single electrons chains with various ET thresholds have also been added for validation the new DNN triggers. The gsf idperf chains originally in this MR have been removed, since issues were found with the current implementation.