Turn Spot VMs to GA on GCE.

[andrewyz]

The SPOT API is released on Apr 20, 2022. To align with this progress, we need to change the SPOT feature from beta to GA.
This is the follow up pull request of #5662
hashicorp/terraform-provider-google#11550

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)

compute: added `provisioning_model` field to `google_compute_instance` resource to support Spot VM

compute: added `provisioning_model` field to `google_compute_instance_template ` resource to support Spot VM

[modular-magician]

Hello! I am a robot who works on Magic Modules PRs.

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@c2thorn, please review this PR or find an appropriate assignee.

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 5 files changed, 191 insertions(+))
TF Validator: Diff ( 4 files changed, 13 insertions(+), 3 deletions(-))

[c2thorn]

/gcbrun

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 5 files changed, 191 insertions(+))
TF Validator: Diff ( 4 files changed, 13 insertions(+), 3 deletions(-))