This merge request merges the changes that went into the ~"21.0" branch between the [release/21.0.87](https://gitlab.cern.ch/atlas/athena/tags/release/21.0.87)
and [release/21.0.88](https://gitlab.cern.ch/atlas/athena/tags/release/21.0.88) tags into the ~"21.3" branch.
It reverts two ~"frozen-tier0-violating" changes from [release/21.0.87](https://gitlab.cern.ch/atlas/athena/tags/release/21.0.87) that introduced large changes
to egamma objects in HI mode: !15622 and !15632.

The release [release/21.0.88](https://gitlab.cern.ch/atlas/athena/tags/release/21.0.88)
was built from the tag [nightly/21.0/2018-11-08T0120](https://gitlab.cern.ch/atlas/athena/tags/nightly/21.0/2018-11-08T0120)

This is the list of merge requests that were included since
the previous release [release/21.0.87](https://gitlab.cern.ch/atlas/athena/tags/release/21.0.87):
 * !15716 : Revert "Merge branch '2-10-18' into '21.0'"
 * !15659 : Pixel DQ hancool protections
 * !15695 : important fix to un-disable 12EM in PbPb2018
 * !15717 : Revert "Merge branch 'HIEU-3-10-2018' into '21.0'"
 * !15674 : Updated Pixel cosmics_run.config
 * !15671 : fix directory structure of JetMon configuration
 * !15664 : Merge branch 'WriteSimOverflowBits' into '21.0'
 * !15655 : 21.0-ISF_FastCaloSim: Created TFCSCenterPositionCalculation class
 * !15645 : Flags for HI jet reconstruction (ATLHI-233)
 * !15611 : fix for ERROR in FTK_DataProviderSvc ATR-18972 and fix to FTK_RawTrack to correctly return InvPt
 * !15536 : PhysicsAnalysis/TauID/: Use TauAnalysisTools truth-matching and selection in Tau Physics Validation
 * !14863 : Adding with DigiTruth info for PFlow
 * !15669 : Update version.txt

Link to the full diff between [release/21.0.88](https://gitlab.cern.ch/atlas/athena/tags/release/21.0.88) and
[release/21.0.87](https://gitlab.cern.ch/atlas/athena/tags/release/21.0.87)
is available at
https://gitlab.cern.ch/atlas/athena/compare/release/21.0.87...release/21.0.88

Former-commit-id: e366e146e24fb31dbfff1bbb589a83ee854a2d14