WIP: feat: allow none platform for tna

[eggfoobar]

Currently two node arbiter supports only baremetal, platform none is also used for baremetal deployments and should be supported. Platform external is also being added as that can be used for baremetal deployments and platform none will be deprecated in the future.

[openshift-ci]

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[openshift-ci]

@eggfoobar: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/okd-scos-e2e-aws-ovn	a4f6650	link	false	/test okd-scos-e2e-aws-ovn

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