Release notes for release/21.0.118

This is the list of merge requests that were included since the previous release release/21.0.117:

!36624 : Externals Update, 21.0 branch (2020.09.22.)
!36642 : Sweeping !36565 from master to 21.0.
!36597 : Sweeping !36550 from 21.2 to 21.0.
!36600 : preInclude file of fractionally charged particles
!36563 : Add overrides for HEC in overlay HI production
!36363 : Fix running trigger int 21.0 with 22.0 RDOs
!36401 : AFP webdisplay [rel 21]
!36345 : Address path resolver issue in ATLASSIM-4674 and store ParamFile in HITS file metadata
!36533 : Sweeping !36482 from 21.2 to 21.0.
!36179 : Add sampling fraction code and analysis for HEC
!36264 : Fix peeking of files with only xAOD::EventInfo
!35986 : Add functionality to find and remove duplicate FastCaloSim instances from the simulation chain
!36140 : Reverting the temporary special reference for HLTtau and restoring default trigger references
!35899 : Sweeping !35830 from master to 21.0.
!35840 : FastCaloSimGAN: skip unused layers early in the GAN layer simulation chain
!35802 : Update log file diff in post.sh