CUDA: small PP performance improvement for MoE models

[ikawrakow]

This PR brings a small (2-3%) prompt processing performance improvement on CUDA for quantized MoE models (when -fmoe is used).

Instead of first copying activations to contiguous memory and the quantizing, quantization is done directly using the row mapping IDs, thus saving the associated kernel launch overhead.

Here is a performance comparison for Q4_0 quantized DeepSeek-Lite on RTX-4080 using -mla 3 -fa -fmoe -b 4096 -ub 4096

Main branch

PP	TG	N_KV	T_PP s	S_PP t/s	T_TG s	S_TG t/s
4096	1024	0	0.480	8532.52	5.640	181.55
4096	1024	4096	0.566	7240.62	5.904	173.43
4096	1024	8192	0.674	6073.99	6.143	166.68
4096	1024	12288	0.789	5189.61	6.421	159.47

PR

PP	TG	N_KV	T_PP s	S_PP t/s	T_TG s	S_TG t/s
4096	1024	0	0.469	8738.41	5.638	181.61
4096	1024	4096	0.554	7388.85	5.909	173.29
4096	1024	8192	0.670	6117.30	6.148	166.57
4096	1024	12288	0.779	5256.86	6.435	159.14