* removed ggml_task_backend, infavour of ggml_task_profile.runner and newly added id and name.
* extracted mul_mat blas codes into ggml_compute_forward_mul_mat_blas,
thus align with CUDA/CL a bit more and make it easier to fix profile and run tune.
* rewrote task profile and update/add some cuda/cl codes, finnaly made CL GPU offloading work.
* misc minor fix/update to tune, the data format was changed.