Use WG kernel module implementation if available

[DasSkelett]

This bumps wg-embed to v0.7.0 to pull in freifunkMUC/wg-embed#9

See the linked pull request for more details.
To repeat the important things:

• We try to use the kernel module, if something throws an error while creating the interface we log it and automatically fall back to the embedded userspace/Go implementation.
• netlink will try to load the kernel module automatically, it only requires CAP_NET_ADMIN (already required for interface management), no CAP_SYS_MODULE or mount of /lib/modules into a Docker container.
  However 1-docker.md still says to load it on the host if possible, as this will be stabler and more future-proof.

You can check the running implementation either by checking for the falling back to embedded Go implementation log line, or running ip -details link show (inside the container). If created through the kernel module the link will show wireguard as first word in the third line, otherwise tun.

[mergeable]

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