[PoC] Restore vpp interfaces

[glazychev-art]

Issue: #512
Tag format: {forwarder-name}_c_{connID}

We try to dump interfaces here to restore them in forwarder.

• We can customize the chain element by adding or not the dump option
• Each element of interest contains dump function which, by tag, determines whether this is "our" interface or not.
• After the dump, a timer is started that will remove the interface if it is "forgotten" (no request with this connectionID)

Elements with a dump implementation here:
-tap
-af_packet
-memif
-vxlan
-L3xc

Additional info

veth pair (af_packet):
We set aliases for kernel veth-pair - https://github.com/networkservicemesh/sdk-vpp/blob/main/pkg/networkservice/mechanisms/kernel/kernelvethpair/common.go#L73.
As I understand, alias format must be the same as tag format. So, probably it's better to add a new chain element, that will add aliases for linux interfaces.
And the veth-pair dump must be through netlink (see kernelvethpair/common.go in this PR)

Open question

Perhaps the order of deletion is important to us. With this approach, we cannot guarantee this.
Probably we should omit deletion after the timeout and use only restore?
Deletion will be if the client calls Close

Signed-off-by: Artem Glazychev [email protected]