ggml-cuda: auto apply iGPU flag for CUDA/HIP if integrated device

[fl0rianr]

Overview

Report CUDA/HIP devices as GGML_BACKEND_DEVICE_TYPE_IGPU when the runtime reports
cudaDeviceProp::integrated.

This intentionally checks cudaDeviceProp directly instead of
ggml_cuda_info().devices[id].integrated, since the latter one is temporally disabled
by design for CUDA buffer allocation behavior due to #15034. So this change only affects the automatic backend
device classification and does not re-enable the integrated-buffer path.

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure:
  NO

[0cc4m]

It's good to see the IGPU type expand to other backends, we can use it to adapt downstream behaviour according to the device type to e.g. disable mmap on integrated GPUs.