cuda : implement bf16 cpy ops and enable bf16 cont

[CISC]

Implemented missing BF16 CPY ops and enabled CONT op for BF16.

Tests before

  CONT(type=bf16,ne=[2,1,1,1]): not supported [CUDA0] 
  CONT(type=bf16,ne=[2,1,3,5]): not supported [CUDA0] 
  CONT(type=bf16,ne=[2,3,5,7]): not supported [CUDA0] 
[...]
  CPY(type_src=bf16,type_dst=bf16,ne=[1,2,3,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[1,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=bf16,ne=[1,2,3,4],permute_src=[0,3,1,2],permute_dst=[0,2,1,3]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=bf16,ne=[2,2,3,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[2,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=bf16,ne=[2,2,3,4],permute_src=[0,3,1,2],permute_dst=[0,2,1,3]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=bf16,ne=[3,2,3,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[3,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=bf16,ne=[3,2,3,4],permute_src=[0,3,1,2],permute_dst=[0,2,1,3]): not supported [CUDA0] 
[...]
  CPY(type_src=f16,type_dst=bf16,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): not supported [CUDA0] 
  CPY(type_src=f16,type_dst=bf16,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): not supported [CUDA0] 
[...]
  CPY(type_src=bf16,type_dst=f32,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=f32,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=f16,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=f16,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=bf16,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): not supported [CUDA0] 
[...]
  CPY(type_src=bf16,type_dst=f32,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): not supported [CUDA0] 
  CPY(type_src=bf16,type_dst=f32,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): not supported [CUDA0] 

Tests after

  CONT(type=bf16,ne=[2,1,1,1]): OK
  CONT(type=bf16,ne=[2,1,3,5]): OK
  CONT(type=bf16,ne=[2,3,5,7]): OK
[...]
  CPY(type_src=bf16,type_dst=bf16,ne=[1,2,3,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[1,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[1,2,3,4],permute_src=[0,3,1,2],permute_dst=[0,2,1,3]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[2,2,3,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[2,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[2,2,3,4],permute_src=[0,3,1,2],permute_dst=[0,2,1,3]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[3,2,3,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[3,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[3,2,3,4],permute_src=[0,3,1,2],permute_dst=[0,2,1,3]): OK
[...]
  CPY(type_src=f16,type_dst=bf16,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=f16,type_dst=bf16,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): OK
[...]
  CPY(type_src=bf16,type_dst=f32,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=f32,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=f16,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=f16,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=bf16,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): OK
[...]
  CPY(type_src=bf16,type_dst=f32,ne=[256,4,4,4],permute_src=[0,0,0,0],permute_dst=[0,0,0,0]): OK
  CPY(type_src=bf16,type_dst=f32,ne=[256,2,3,4],permute_src=[0,2,1,3],permute_dst=[0,0,0,0]): OK

Also fixed a cut'n'paste error for F16->F16 in ggml_cuda_cpy_fn and deduplicated all copy functions.

[JohannesGaessler]

Generally speaking I am not a fan of how the float conversions are being done currently. I think the code could be deduplicated significantly by unconditionally casting half, nv_bfloat16, and float to float and then simply using that float value to set the destination. I would appreciate it if you were to do this in this PR, otherwise I'll keep it as one of the tasks to hand out when people ask me for a good first issue to work on.