The issue is not so easy to fix, as GRPC tunnel on/off change requires
two different flow for the link (interface):
* no tunnel -> Talos link controller should create in-kernel `wireguard`
link and no userspace components
* tunnel on -> Talos link controller should never create the link, and
only adjust WG settings via UAPI, while the actual link is created by
the userspace implementation (it's a `tun` device)
Transition between those two links is impossible for the link controller
to distinguish, as it doesn't know that it has to drop old link and skip
creating new one based on the information available.
So, instead, use different names for the link in two states:
`siderolink` for the kernel flow, and `siderolinktun` for the userspace
flow. This fixes the issue of proper link cleanup/re-creation.
Add integration tests.
Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>
