chore!(amneziawg): refactor to be separate from wireguard

- amneziawg is now a VPN protocol and no longer a Wireguard implementation
- Use it with VPN_TYPE=amneziawg
- document AMNEZIAWG_* options in Dockerfile
- document amneziawg support in readme
- separate amneziawg settings and code from wireguard
- re-use code from wireguard whenever possible

.golangci.yml

@@ -60,6 +60,10 @@ linters:
       - linters:
           - lll
         source: "^// https://.+$"
+      - linters:
+          - mnd
+        source: "^	cleanups\\.Add.+$"
+        path: internal\/(wireguard|amneziawg)\/run\.go
       - linters:
           - err113
           - mnd