Q4_0_R4 on CUDA

[ikawrakow]

With the massive improvements in prompt processing speed on the CPU achieved via interleaving 4 tensor rows (see #118, #119, #120, #121, #122, #123, #124), I was curious to see if one can get a good implementation for the X_R4 quants on CUDA. This PR is a POC that implements CUDA dequantization and matrix x vector multiplication for Q4_0_R4. It achieves the same TG speed as Q4_0. It was disappointing to not get a speedup via row interleaving, but at least there is no performance regression. To make it a full PR I should also implement quantized matrix x matrix multiplication for Q4_0_R4 (here it is done via dequantize to f16 and cuBLAS, so it is slower than Q4_0 MMQ).