[WIP] NekRS + Ascent for In-Situ Visualization

[yslan]

This is a working in progress draft PR preparing for the next release. Original code is from Victor Mateevitsi (@mvictoras)

Feature

Enable on-the-fly visualization directly rendered on device without any DtoH copies. This further reduces the data footprint (runtime, storage, paraview I/O) at large scale.

TODO

Necessary changes

• [x] put mesh_data into name space
• [ ] Use mempool and only re-allocating if needed.
• [ ] assign backend? allow mixed backend (via extra DtoH copies)?
• [ ] a better timer?
• [ ] verbose mode, print available fieldName, TODO, check vel_mag?
• [ ] reduce yaml files
• [ ] Clean up code. May need several iterations
• [ ] A cleaner script. There must be a better way to set the INCLUDE / LIB FLAGS
• [ ] Provide more example (link to external repository) and gallery. Meanwhile, the pb146 example doesn't have other fancy feature. We should just use it.
• [ ] A README to simply explain what is what.

Features

• [x] Support "default mode", like in tavg, auto use all active fields.
• [ ] map2reg, at other N (crucial for "noisy fields", like the contour of lambda2)
• [ ] cht
• [ ] neknek?
• [ ] particles?
• [x] dfloat = fp32

Tests

• [x] Laptop / Linux server (CPU)
• [ ] Laptop with docker env (CPU)
• [x] Polaris CUDA (both float=fp64 or fp32)
• [x] Frontier OpenMP (Ascent module v0.8.0)
• [x] Frontier HIP (Ascent module v0.9.2)
• [ ] performance?