promote node_pool_auto_config field to GA provider

[jeperetz]

Fixes hashicorp/terraform-provider-google#15834.

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• 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).
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Release Note Template for Downstream PRs (will be copied)

container: promoted `node_pool_auto_config` field in `google_container_cluster` from beta provider to GA provider. (ga)

[modular-magician]

Hello! I am a robot. It looks like you are a: Community Contributor Googler Core Contributor. Tests will run automatically.

@melinath, a repository maintainer, has been assigned to review your changes. If you have not received review feedback within 2 business days, please leave a comment on this PR asking them to take a look.

You can help make sure that review is quick by doing a self-review and by running impacted tests locally.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 3 files changed, 179 insertions(+), 3 deletions(-))
Terraform Beta: Diff ( 1 file changed, 3 insertions(+), 3 deletions(-))

[melinath]

Running GA tests manually since this is a promotion: https://hashicorp.teamcity.com/buildConfiguration/TerraformProviders_Google_MmUpstreamTesting_GOOGLE_PACKAGE_CONTAINER/27923?hideProblemsFromDependencies=false&hideTestsFromDependencies=false

[melinath]

LGTM - only failing test also fails in the nightly builds.