Make shader clip space consistent across APIs and projection matrices.

- All shaders are expected to output clip space values that are effectively y-up, with [-1, 1] z, in NDC.
- The transform to a backend's expected clip space values from the above range now happens after user vertex shader code is run, instead of inside a projection matrix.
- Projection matrices no longer need to be flipped when rendering to a canvas versus the main screen.

This means custom projection matrices might need to be altered to account for the more consistent range.

src/modules/graphics/metal/Graphics.mm

@@ -465,12 +465,6 @@ love::graphics::GraphicsReadback *Graphics::newReadbackInternal(ReadbackMethod m
 	return new GraphicsReadback(this, method, texture, slice, mipmap, rect, dest, destx, desty);
 }
 
-Matrix4 Graphics::computeDeviceProjection(const Matrix4 &projection, bool /*rendertotexture*/) const
-{
-	uint32 flags = DEVICE_PROJECTION_FLIP_Y;
-	return calculateDeviceProjection(projection, flags);
-}
-
 void Graphics::backbufferChanged(int width, int height, int pixelwidth, int pixelheight, bool backbufferstencil, bool backbufferdepth, int msaa)
 {
 	bool sizechanged = width != this->width || height != this->height
@@ -1133,6 +1127,9 @@ void Graphics::applyShaderUniforms(id<MTLRenderCommandEncoder> renderEncoder, lo
 	// Same with point size.
 	builtins->normalMatrix[1].w = getPointSize();
 
+	uint32 flags = Shader::CLIP_TRANSFORM_Z_NEG1_1_TO_0_1;
+	builtins->clipSpaceParams = Shader::computeClipSpaceParams(flags);
+
 	builtins->screenSizeParams = Vector4(getPixelWidth(), getPixelHeight(), 1.0f, 0.0f);
 	auto rt = states.back().renderTargets.getFirstTarget();
 	if (rt.texture.get())