Updated UpCloud terraform script to use private network and dynamic additional disks

[Xartos]

What type of PR is this?

/kind feature

What this PR does / why we need it:

To be able to set up more complex kubernetes clusters in UpCloud, I added the ability to add additional data disks as well as a private network to segregate private and public traffic.

Which issue(s) this PR fixes:

Fixes none

Special notes for your reviewer:

Previously there were a hostname variable, which I assume was to separate environments. I have now changed that in favor of a prefix variable, to harmonize with the rest of the terraform scripts in this repo. Although I made it possible to still keep the same name if you set the prefix variable to "" and add the hostname to each nodename instead.

Does this PR introduce a user-facing change?:

Removed hostname variable in favor of prefix in the upcloud terraform provider

[k8s-ci-robot]

Hi @Xartos. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[Xartos]

@ewnetu PTAL

[oomichi]

/ok-to-test

[floryut]

/cc @oomichi @EppO

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: floryut, Xartos

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• contrib/terraform/OWNERS [floryut]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[floryut]

@Xartos should we close this one #7531 ?

[oomichi]

/lgtm