NCC in 2-net-a-simple

[sruffilli]

• Ran terraform fmt on all modified files
• Regenerated the relevant README.md files using tools/tfdoc.py
• Made sure all relevant tests pass
• Updated README.md to reflect the changes

This is a first, basic implementation of NCC in 2-simple.

Caveats:

1. Landing is not part of the core network anymore, but it simply hosts hybrid connectivity, which itself is connected as a spoke
2. Because of (1), do we need a "shared services" VPC?
3. VPC spokes must be authorized manually (i.e. from the Cloud Console). At this stage the terraform provider (nor the API?) does not allow for ncc hub projects allowlisting.

[LucaPrete]

Minor comments.
For ncc we shouldn't need to be whitelisted, given it just went public preview. Anyway, the provider is not there yet.
Also, readme should be updated before merge.

[ludoo]

really linear and simple to read :)

[sruffilli]

Minor comments. For ncc we shouldn't need to be whitelisted, given it just went public preview. Anyway, the provider is not there yet.

This PR is tested and it works :)
The provider didn't really require any change, as the new feature allows for the NCC-Hub to have BOTH VPC spokes and Hybrid connectivity spokes.

Also, readme should be updated before merge.

This is why the PR is in draft. I'm updating the README as/if we reach consensus this is a valid PR.

[LucaPrete]

lgtm now. I guess we can finalize this updating tests and readme and then merge.

[sruffilli]

Given there seems to be consensus, I'll go ahead and write docs/tests.