feat(GKE): add reservation samples

[apeabody]

Description

add GKE reservation samples

Checklist

Readiness

• Yes, merge this PR after it is approved
• No, don't merge this PR after it is approved

Style

• My sample follows the rules described for Terraform in the Effective Samples style guide
• My sample follows the other requirements and best practices in the Contributing
  guide

Testing

• I have performed tests described in the Contributing guide:

  • Tests pass: terraform apply
  • Lint pass: terraform fmt check

Intended location

• Yes, this sample will be (or already is) included on cloud.google.com
  Location(s): https://cloud.google.com/kubernetes-engine/docs/how-to/consuming-reservations

• No, this sample won't be included on cloud.google.com
  Reason:

API enablement

• If the sample needs an API enabled to pass testing, I have added the service to the Test setup file

Review

• If this sample adds a new directory, I have added codeowners to the CODEOWNERS file

[snippet-bot]

Here is the summary of changes.

You are about to add 9 region tags.

• gke/autopilot/reservation/main.tf:30, tag gke_autopilot_reservation_specific_reservation
• gke/autopilot/reservation/main.tf:52, tag gke_autopilot_reservation_specific_cluster
• gke/autopilot/reservation/main.tf:86, tag gke_autopilot_reservation_specific_pod
• gke/autopilot/reservation/main.tf:139, tag gke_autopilot_reservation_specific_accelerator
• gke/standard/zonal/reservation/main.tf:17, tag gke_standard_zonal_reservation_any_reservation
• gke/standard/zonal/reservation/main.tf:32, tag gke_standard_zonal_reservation_any_cluster
• gke/standard/zonal/reservation/main.tf:57, tag gke_standard_zonal_reservation_any_node_pool
• gke/standard/zonal/reservation/main.tf:74, tag gke_standard_zonal_reservation_specific_reservation
• gke/standard/zonal/reservation/main.tf:91, tag gke_standard_zonal_reservation_specific_node_pool

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[glasnt]

Unrelated CI failure. Will try re-running.

[glasnt]

/gcbrun

[apeabody]

(re-triggered from another flake)

[apeabody]

The repeated CI failure is from an unrelated GKE sample. Moved my experiment on finer test filtering to #669