Upcloud: Added support for routers and gateways

[Xartos]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change /kind bug /kind cleanup /kind design /kind documentation /kind failing-test /kind feature /kind flake

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

I will wait for this PR to be merged, then I'll rebase it. So you only need to look at this commit

Does this PR introduce a user-facing change?:

terraform: Added support for UpCloud routers and gateways