SIMD enhanced std::lower_bound

[mlund]

Non-bonded interactions can currently be splined and during lookup std::lower_bound() is used to find the knot. It however performs poorly with SIMD and we could instead investigate the following method which may be 10x faster:

• https://en.algorithmica.org/hpc/data-structures/s-tree/#implicit-b-tree-1
• https://www.youtube.com/watch?v=1RIPMQQRBWk
• Somewhat related: https://quickwit.io/blog/search-a-sorted-block