gpu: switch from uniform buffers to combined push buffers

Vulkan doesn't support changing uniforms during a render pass. However,
push constants *can* be changed. The gio-shader repository was changed
to use push constants instead of uniforms, this change implements the
corresponding driver and renderer change.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/internal/driver/driver.go

@@ -43,8 +43,7 @@ type Device interface {
 	BindVertexBuffer(b Buffer, offset int)
 	BindIndexBuffer(b Buffer)
 	BindImageTexture(unit int, texture Texture, access AccessBits, format TextureFormat)
-	BindVertexUniforms(buf Buffer)
-	BindFragmentUniforms(buf Buffer)
+	BindUniforms(buf Buffer)
 	BindStorageBuffer(binding int, buf Buffer)
 
 	BeginCompute()