Links information module for shared state according to babeld

[javierbrk]

This module incorporates links information extracted from babel using ubus infrastructure. The module has been tested in two librerouters and the output of the shared-state-async get babel_links_info in my setup is

    "lrprimero": [
        {
            "dst_ip": "fe80::aa40:41ff:fe1f:73ab",
            "iface": "eth1-2_17",
            "src_ip": "fe80::aa40:41ff:fe1f:723b"
        },
        {
            "dst_ip": "fe80::c24a:ff:fefc:3abd",
            "iface": "eth1-2_17",
            "src_ip": "fe80::aa40:41ff:fe1f:723b"
        }
    ],
    "lrsegundo": [
        {
            "dst_ip": "fe80::aa40:41ff:fe1f:723b",
            "iface": "eth1-2_17",
            "src_ip": "fe80::aa40:41ff:fe1f:73ab"
        },
        {
            "dst_ip": "fe80::c24a:ff:fefc:3abd",
            "iface": "eth1-2_17",
            "src_ip": "fe80::aa40:41ff:fe1f:73ab"
        }
    ]
}

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 79.59%. Comparing base (4dc7f98) to head (f442b02).

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1056 +/- ## ========================================== + Coverage 79.56% 79.59% +0.03% ========================================== Files 53 53 Lines 4566 4568 +2 ========================================== + Hits 3633 3636 +3 + Misses 933 932 -1 ```

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[G10h4ck]

should be ported to shared-state-async before merging