Separate 1D mipmap generation support from rendering into an 1D texture.
Those are two independent features, so have a separate feature flag for
both instead of using just one.
This will then be symmetric with the 3D texture features, where now we
have a new flag to report support for generating mipmap for 3D textures.
(whereas 3D texture as a render target is already covered by
RenderTo3DTextureSlice)
Change-Id: Ie5e1f056a7d1c341d90cd7fc522877a3f2da3290
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
9c84036d4f