Add LAPACK functions for Nonsymmetric Eigenvalues Problems

[albertomercurio]

Hello,

I think it could be great to add some of the LAPACK functions for Nonsymmetric Eigenvalues Problems.

Most of them are yet implemented, but I noticed that for example hseqr (which finds the eigenvalues and Schur factorization of an Hesenber matrix) is not yet present.

[albertomercurio]

I think it is not so difficult to implement. The KrylovKit package did it on his own.

https://github.com/Jutho/KrylovKit.jl/blob/dee29fe34c724e4c9532ea22dfb6e0464263b8c1/src/dense/linalg.jl#L499

[ViralBShah]

If you could, please submit a PR. Happy to accept.