platform: allow CLC templating for dynamic IP address insertion

[pothos]

• platform: allow CLC templating for dynamic IP address insertion
  The tests that require coreos-metadata and CLC templating could not
  run because for QEMU only a static replacement was done before the
  CLC configuration was rendered.
  Add support for the template variables by treating QEMU as a custom
  platform for the transpiler, making use of a coreos-metadata service
  that has the IP addresses hardcoded.

• platform/machine/*/cluster.go: update custom coreos-metadata service

  The coreos-metadata service in the Flatcar OEMs normally writes to
  a "flatcar" file and symlinks it.
  Do the same for the custom ESX and QEMU coreos-metadata services.

• platform/local/dnsmasq: hardcode DNS server for QEMU tests

  The system may have 127.0.0.53 as DNS server which is the
  systemd-resolved stub. This is no reachable from the dnsmasq's
  network namespace which has its own loopback interface.
  Hardcode the DNS servers to Cloudflare's and Google's to ensure
  DNS is working regardless of the host /etc/resolv.conf file.

• kola/tests/*: enable more tests for QEMU

How to use/testing done

Run QEMU tests for

cl.locksmith.cluster cl.etcd-member.discovery cl.etcd-member.v2-backup-restore cl.etcd-member.etcdctlv3 cl.flannel.vxlan cl.flannel.udp coreos.ignition.security.tls

[tormath1]

LGTM ! Thanks :)