VTKHDF/vtkHDFReader: add temporal overlappingAMR

Context

It isn't possible to store temporal overlapping AMR with the VTKHDF File Format 2.1.

Solution

A proposal on discourse has been made here. In short, we add an intermediary group between Step and Point/Cell/FieldDataOffsets named LevelX where X is the current level. Additional datasets has been added to store temporal AMRBox:

• AMRBoxOffsets : to retrieve for the current timestep where we should start to read the AMRBox
• NumberOfAMRBox : to retrieve for the current timestep, the number of box contained in the AMRBox

Diagram for temporal OverlappingAMR

Contents

• make a proposal regarding this use case : https://discourse.vtk.org/t/vtkhdf-support-transient-data-for-overlappingamr/13123
• update the spec
• Update the vtkHDFReader to support this use case by retrieving each offset arrays for each level.
• update the vtkhdf-scripts repository and use it for the testing in vtk : keu-public/vtkhdf/vtkhdf-scripts!3 (merged)

Others

• rename, in doc and class, transient to temporal as we don't use the correct term which is ambiguous