Adapting for use with latest providers

[brandonjbjelland]

What's in this change?

1. The core fix was removing the node_pool inline block in favor of the now supported initial_node_count.
2. resources and data lookups now use location instead of zone or region to get remove deprecation warnings.
3. aligning helper script combine_docfiles.py with upstream.

Why make the change?

The motivation here started with being unable to use the module as is at the v2.0.0 release. The node-pool inline block was the source of this error:

Error: Error applying plan:

1 error(s) occurred:

* module.gke.google_container_cluster.primary: 1 error(s) occurred:

* google_container_cluster.primary: googleapi: Error 400: Cluster.initial_node_count must be greater than zero., badRequest

Replacing zone and region with location was motivated by wanting to resolve deprecation warnings:

Warning: module.gke.data.google_container_engine_versions.region: "region": [DEPRECATED] Use location instead
Warning: module.gke.data.google_container_engine_versions.zone: "zone": [DEPRECATED] Use location instead
Warning: module.gke.google_container_cluster.primary: "region": [DEPRECATED] Use location instead
Warning: module.gke.google_container_node_pool.pools: "region": [DEPRECATED] use location instead

Note: With the new location attribute available, it's possible (though a breaking change) we could also move both regional and zonal clusters and pools to be the same resources rather than spread them across two flavors. I didn't do that here because it's rather impactful but potentially a direction to take this next in simplifying.

Fixes #143

[morgante]

Thanks for the contribution! LGTM, but can you verify whether this is a breaking change for existing clusters?

[morgante]

Looks like upgrades are breaking and CI is failing.

[brandonjbjelland]

We're in a conflicting state here and since my current client is not looking to even use this module, it's exceedingly difficult to find the time to follow through. If that decision changes (through pain) or some time clears up, I'll revisit this work.