Vulkan: Use compute shader for non-indirect unsupported topology index buffer conversions

Unmerged PR from OG Ryujinx (#7268). From Isaac Marovitz:

Previously, this shader was only used for indirect draws with unsupported topologies, even though it works just fine on traditional draws, too.

This should significantly speed up this process on MoltenVK, as the tiny copies used before could not be performed by a MTLBlitCommandEncoder and instead required a compute dispatch each.