Support indirect draw/compute

[Try]

API:

• drawIndirect
• drawIndexedIndirect
• dispath
• dispatchMesh

GLSL:

• gl_VertexIndex and gl_InstanceIndex
  • Just works on Metal (afaik)
  • fist-instance has only 90% coverage (and some 2023 devices do not support it)
  • Just doesn't work in DX
• gl_NumWorkGroups
  • Should work on metal (?)
  • Just works on Vulkan
  • Just doesn't work in DX - can be emulated with push-descriptor

Alignment:
offset must be multiple of 4 in Vulkan
offset must be multiple of 4 in DX12 (https://learn.microsoft.com/en-us/windows/win32/api/d3d12/nf-d3d12-id3d12graphicscommandlist-executeindirect#remarks)
offset in Metal "check for offset alignment requirements for buffers in device and constant address space." - not documented(?!)

[Try]

DX12 flickers on NVidia:

^ gothic2 oldworld.zen

Seem to be a cache-coherency bug; maybe need to report to NV