feat: Bump to C++20 and update TPLs

[victorapm]

• Move minimal supported C++ standard from C++17 to C++20
• Update TPLs (VTK 9.7, RAJA suite 2026, fmt 12) and update geos codebase accordingly
• Add ROCm build-only (no executed tests) to CI testing
• Bump blt to 0.7.2
• Fix various CMake warnings

Depends on GEOS-DEV/thirdPartyLibs#361
Depends on GEOS-DEV/LvArray#356

[dkachuma]

I'm a bit confused here. Since we are not enforcing C++20, shouldn't we always use <format>?

[victorapm]

Hi Dick, this branch is enforcing C++20, but {fmt} remains intentional because GEOS uses fmt::runtime, fmt::join, fmt::is_formattable and custom fmt::formatter. Also, <format> is not uniformly supported by the CUDA/HIP backends. Maybe we can address this on a separate PR

[victorapm]

Rebaseline needed because of a baseline mismatch (3051 vs 3095 faces) caused by the VTK 9.4.2 → 9.7.0 upgrade

[jafranc]

Great work @victorapm

It start having quite some patch for this or that compiler depending on the version. Would it worth having a page in the doc stating those ?

[victorapm]

Thanks, Jacques! You mean the checks on the vtk version? If so, I think we can remove those and just support the path for the newest version (9.7.0)