Ip allocator refactoring

We don't need ordered set anymore, also some cleanings and simple
benchmark.
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Merge pull request #5937 from LK4D4/ipallocator_refactoring

Ip allocator refactoring