WIP: network_manager: Assign routes to ip section by ip version

[holmanb]

Fixes GH-4518

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Fixes GH-NNNNN (GitHub Issue number. Remove line if irrelevant)
LP: #NNNNNN (Launchpad bug number. Remove line if irrelevant)

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• I have updated or added any unit tests accordingly
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[TheRealFalcon]

When running this against the original yaml file, I get:

[connection]
id=cloud-init eth0
uuid=1dd9a779-d327-56e1-8454-c65e2556c12c
autoconnect-priority=120
type=ethernet
interface-name=eth0

[user]
org.freedesktop.NetworkManager.origin=cloud-init

[ethernet]

[ipv4]
method=auto
may-fail=false
route1=169.254.42.42/32,62.210.0.1

[ipv6]
method=manual
may-fail=false
address1=2001:bc8:1210:232:dc00:ff:fe20:185/64

Rather than move to the ipv6 section, the v6 route has disappeared.

While we're here, we should ensure the other fields are working too, and dns-search is also incorrect. With an updated yaml:

version: 2
ethernets:
  eth0:
    dhcp4: true
    nameservers:
      search: [lab, home]
      addresses: [8.8.8.8, FEDC::1]
    routes:
      - to: 169.254.42.42/32
        via: 62.210.0.1
      - via: fe80::dc00:ff:fe20:186
        to: ::/0
    addresses:
      - 192.168.1.20
      - 2001:bc8:1210:232:dc00:ff:fe20:185/64

the resulting [ipv6] section has no dns-search.

Also, unit test please.

[holmanb]

Closing in favor of @TheRealFalcon's solution.