Vulkan Bugfixes and Improvements (llama/7084)

Vulkan Bugfixes and Improvements (llama/7084)

* Modify mat mat mul shader for mul_mat_id, modify mat vec mul shaders for single call batch operation

* Further work towards MoE, disabled for now

* Disable MoE code (not ready yet), fix a number of bugs in shaders and Vulkan code

* Add softmax with f16 mask and pos buffer support

* Disable mul_mat_id shaders for now

* Fix flake8

* Fix validation errors caused by empty buffers on larger batch sizes