Add GKE Multicloud

[modular-magician]

This PR adds GKE Multicloud to Terraform, via the DCL.

A few notes of complexity here:

• This resource caused a separation in the DCL of struct name and resource name, which required some changes to name manipulation in TPGTools. A follow-on PR is coming to address that.
• This resource has the first DCL-bridge regional endpoint, so we needed to use replaceVars to get the location out before sending it to the DCL.
• Some of the samples are hand-edited, because Terraform can't easily perform the necessary operations to update and replace a Client. Those updates are tested in the DCL but can't be easily tested here.
• These resources require a ton of novel variables because they are designed to use things set up in other clouds.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

google_container_azure_client

google_container_azure_cluster

google_container_azure_node_pool

google_container_aws_cluster

google_container_aws_node_pool

google_container_aws_versions

google_container_azure_versions

Derived from GoogleCloudPlatform/magic-modules#5522

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