The previous method would cause OOB reads for the last row to clamp, and adding an extra row would potentially encounter unmapped memory. So use this technique based on how Ryu does it.
It is desirable for us to use a shader for blits to allow easily emulating out of bounds blits and blits between different swizzled colour formats. The helper shader infrastructure is designed to be generic so it can be reused by any other helper shaders that we may need in the future.
