Delete and recreate pinned maps in case of mismatch with the map's spec

[jibi]

To address cilium/cilium#15629 I need to delete and recreate a pinned map in case there's a mismatch with the map's spec and the actual pinned map (type, k/v size, flags etc).

I see 2 approaches :

• have this logic in cilium/ebpf by introducing a new option in MapOptions.LoadPinOptions. If there's a mismatch and the option is set, NewMapWithOptions will delete the existing map and try to recreate it.
  Code changes are small but I'm not sure if this logic would be too specialized/high level for the package.
• have this logic in cilium/cilium. The caller of ebpf.NewMapWithOptions would be responsible for detecting the mismatch, deleting the map and recreating it.
  My concern here would be on detecting the mismatch, as the best I could come up with is:

newMap, err := ebpf.NewMapWithOptions(spec, opts)
if err != nil {
    if strings.HasPrefix(err.Error(), "use pinned map ") {
        // delete the map and call again NewMapWithOptions

which to me looks fragile 😕

[jibi]

We agreed on Slack to introduce for now a new ErrMapIncompatible error and return that from New{Map,Collection} in order to enable the caller to properly detect when there's a mismatch