Migrate dlib/cmake_utils/find_blas.cmake to FindBLAS

[sheldonrobinson]

Main idea

Can we use CMake module FindBLAS instead of find_blas.cmake. Prior blocker was support for cmake <= 3.17 but that seems to be no longer an issue after migration to FindCudaToolkit, see #2833.

Anything else?

[davisking]

Yeah, if you want to send me a PR for it that would be great :D

It does need to continue to be as capable as the existing find blas cmake code though. I haven't used the new FindBLAS, so I don't know if it's covering as much ground. But for instance, the current script we have handles matlab integration and finding blas on windows. It would not surprise me if those use cases were ignored (or largely ignored to the point that users perceive that it doesn't cater to those use cases by default) by the built in FindBLAS.