cgroups/ebpf: switch to new cilium/ebpf API

[kolyshkin]

cilium/ebpf's prog.{Attach,Detach} API is now deprecated in favor of new link package (see cilium/ebpf@5727d65 and cilium/ebpf#110).

runc need to adopt.

libcontainer/cgroups/ebpf/ebpf.go:35:12: SA1019: prog.Attach is deprecated: use link.RawAttachProgram instead.  (staticcheck)
	if err := prog.Attach(dirFD, ebpf.AttachCGroupDevice, unix.BPF_F_ALLOW_MULTI); err != nil {
	          ^
libcontainer/cgroups/ebpf/ebpf.go:39:13: SA1019: prog.Detach is deprecated: use link.RawDetachProgram instead.  (staticcheck)
		if err := prog.Detach(dirFD, ebpf.AttachCGroupDevice, unix.BPF_F_ALLOW_MULTI); err != nil {
		          ^

I don't know much about these matters; @cyphar mind to take a look?

[thaJeztah]

missed there was a tracking issue for this; I opened #2903, which also revealed a potential bug in the closer (pls double-check that one)