CLDawes

metal: add ops DIAG_MASK_INF, IM2COL_3D, fix op PAD

1

I wrote this to fix a problem I was having working with [leejet/stable-diffusion.cpp](https://github.com/leejet/stable-diffusion.cpp). It may fix issues that other people are having, such as their [#850](https://github.com/leejet/stable-diffusion.cpp/issues/850) and [#857](https://github.com/leejet/stable-diffusion.cpp/issues/857). As a...