Hackathon project08: Preserve moved array storage in VoxelsOnCartesianGrid for CUDA-managed images

[Dimitra-Kyriakopoulou]

This PR is PART of Hackathon Project 8: update STIR data to CUDA managed pointers, then adapt sirf.STIR data-containers (images first) and expose the underlying CUDA managed pointer to Python. This PR contains the STIR part of that work. The companion SIRF changes are in the fork under Dimitra-Kyriakopoulou/SIRF on branch Hackathon_Project8, and the runnable end-to-end benchmark is in the separate repository Dimitra-Kyriakopoulou/hackathon_project_08_stir_cuda_managed_pointers.

Changes in this pull request

• VoxelsOnCartesianGrid now preserves moved array storage instead of forcing the storage through the old copy path during image construction.
• This is the low-level STIR change needed so that managed-memory-backed image data can survive the STIR container construction path.
• The scope is intentionally narrow and standalone at STIR level.

Role

• Project 8 is not only about a Python handle; it first needs STIR image containers to stop losing the managed-memory storage.
• Without this change, the managed pointer path breaks before SIRF/Python can expose it.

Testing performed

• These are targeted CUDA validation probes, not yet integrated into the permanent STIR ctest suite.
• managed_array_probe.cu: verifies that cudaMallocManaged-backed storage can be wrapped by stir::Array<3,float>, updated, and read back correctly.
• managed_voxels_probe.cu: verifies the same for stir::VoxelsOnCartesianGrid.
• managed_voxels_sptr_probe.cu: verifies the actual patch point, namely that the VoxelsOnCartesianGrid construction/shared-pointer path preserves the managed storage instead of copying it away.

Related issues

Checklist before requesting a review

• [] I have performed a self-review of my code
• [] I have added docstrings/doxygen in line with the guidance in the developer guide
• [] I have implemented unit tests that cover any new or modified functionality (if applicable)
• The code builds and runs on my machine
• [] documentation/release_XXX.md has been updated with any functionality change (if applicable)

Contribution Notes

Please tick the following:

• [ x] The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in STIR (the Work) under the terms and conditions of the Apache-2.0 License.
• I (or my institution) have signed the STIR Contribution License Agreement (not required for small changes).

[KrisThielemans]

merging master first, but looks good.

[Dimitra-Kyriakopoulou]

Dear Professor @KrisThielemans,
THANK YOU WHOLEHEARTEDLY!!!
Dimitra

[KrisThielemans]

appveyor fix to use libparallelproj=1 (as opposed to skipping it), pending #1689