backport multiple fixes
Backport from master these bug fixes:
- fix return type of a method in the contour filter : !10821 (merged)
- fix uninitialized value in HandleRepresentation : !10877 (merged)
- fix wrong property display in a vtkErrorMacro in vtkDataObjectToConduit : !10886 (merged)
- fix race condition in cell derivatives filter : !10874 (merged)
- fix bad method used to retrieve neighbor tree in HTG GCG : !10881 (merged)
backport: release
Edited by Lucas Givord