Add bounds checks to lax

[jturner314]

For the methods in the lax crate which call LAPACK, we need to either add bounds checks (i.e. checking that the provided layout will not cause an out-of-bounds read for the corresponding slice) or make the methods unsafe.

My preference would actually be to change the API, introducing LapackArrayView and LapackArrayViewMut types which combine the layout and slice together into a single type and have checked conversions from ndarray::ArrayBase.