``numpy.linalg`` typing improvements and preliminary shape-typing support

numpy.linalg typing improvements and preliminary shape-typing support

Input and output dtypes for numpy.linalg functions are now more precise. Several of these functions also gain preliminary shape-typing support while remaining backward compatible. For example, the return type of numpy.linalg.matmul now depends on the shape-type of its inputs, or fall back to the backward-compatible return type if the shape-types are unknown at type-checking time. Because of limitations in Python's type system and current type-checkers, shape-typing cannot cover every situation and is often only implemented for the most common lower-rank cases.