ImGuizmo: Support infinite-far-plane reversed-z

[troughton]

It is possible to create valid projection matrices where the far plane is at infinity, in which case the ray direction will be NaN. We can avoid this by shifting the far plane closer in NDC space.

[m-schuetz]

Thanks for that pointer. This, together with hardcoding gContext.mReversed = true in ComputeContext() made it work for me. I'm also using projection matrix with reverse-z and infinite far.

[hrydgard]

I had to do the same, the reverse detection doesn't work.

For reference, here's my proj matrix (Vulkan):

void Matrix4x4::SetProjectionInfReverse(float near_plane, float fov_vert, float aspect) {
	clear();
	float f = 1.0f / tanf(fov_vert * 0.5f);
	xx = f / aspect;
	yy = f;
	wz = near_plane;
	zw = -1.0f;
}

As a side note, with fp32 Z, today there's really no reason to use any other projection matrix than this. It achieves great distribution over the numeric range, and far planes are effectively obsolete. And even fits in a float4... you don't need a full matmul.