Motivation for this change

libibverbs and librdmacm are outdated and have been replaced by the package rdma-core. Their latest version in nixpkgs was from 2014 (https://downloads.openfabrics.org/verbs). All dependencies to these two packages have now been removed in nixpkgs (#34314).

rdma-core contains up-to-date versions of both libraries.

See #33090 and #34314 for details.

Things done

Removed both packages.

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Fits CONTRIBUTING.md.