for QgsVectorLayer, when constructing a layer with a URI which
may be invalid
These may be used for layers where the geometry type/CRS is
known in advance, and where the layer path may not be
initially resolvable. (E.g. layers with a URI pointing to a
non-existant file). It is only ever used if the layer cannot
be resolved, otherwise the actual layer geometry type will be
detected and used for the layer.
