add new terraform docs

[jubrad]

Motivation

Revival of Jun's Pr to shift the cloud specific terraform install and upgrade structure +docs for the new terraform.

[SangJunBak]

@jubrad thanks for reviving this!

[jubrad]

@kay-kim couple of thoughts on the new changes to the docs that should 100% not delay merging

1. The doc is more tutorialized, which is probably good, but is no longer synced in any way to the TF docs on the terraform mono repo meaning they will not be kept up-to-date unless someone manually reconciles the two different doc streams. We need to either up-stream this or commit to a lot of toil keeping these in sync.
2. I think we should be more explicit that install on pages are an example using our terraform, and that it is not required at all to use our terraform to install on any cloud provider.

[maheshwarip]

Thanks for all your work here @jubrad and @kay-kim - this is a really big PR and a big step forward!

[maheshwarip]

Going to pre-approve so that we're unblocked