Allow specifying inner & outer stride for CWiseUnaryView - fixes #2398

Reference issue

#2398 (closed)

What does this implement/fix?

This MR adds the ability to manually specify the inner and/or outer stride for CWiseUnaryView, to avoid issues caused by the incorrect automatic derivation of strides. The strides are set in an identical manner to Map, via:

CwiseUnaryView<view_op, VectorType, Stride<OuterStride,InnerStride>> vec_view(vec);

Additional information

Tests are added to check that strides are set correctly