dhcpcd: Install and configure dhcpcd

`dhcpcd` is a fully-featured network manager, without all the bloat of
`NetworkManager`.

roles/dhcpcd/defaults/main.yml

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+dhcpcd_send_hostname: true
+dhcpcd_use_clientid: false
+dhcpcd_persistent: true
+dhcpcd_rapid_commit: true
+dhcpcd_options: '{{ dhcpcd_default_options }}'
+dhcpcd_ntp_servers: true
+dhcpcd_interface_mtu: true
+dhcpcd_require_server_id: true
+dhcpcd_slaac_private: true
+dhcpcd_noipv4ll: false
+dhcpcd_noipv4: false
+dhcpcd_noipv6rs: false
+dhcpcd_interfaces: []