Add support for configuring disk resource policies for google_compute_instance_template

[ScottSuarez]

Fixes hashicorp/terraform-provider-google#6719

upstreams hashicorp/terraform-provider-google#8237

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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).
• 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 `disk.resource_policies` field to resource `google_compute_instance_template`

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[modular-magician]

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

Diff report:

Terraform GA: Diff ( 4 files changed, 127 insertions(+), 13 deletions(-))
Terraform Beta: Diff ( 5 files changed, 128 insertions(+), 14 deletions(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=170850"

[melinath]

LGTM - I think there's a thing where data sources are supposed to refer to the resources docs for full field documentation? But I don't remember the details and I think this is also fine.

[melinath]

/gcbrun - previous run failed due to instance issue

[modular-magician]

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

Diff report:

Terraform GA: Diff ( 4 files changed, 127 insertions(+), 13 deletions(-))
Terraform Beta: Diff ( 4 files changed, 127 insertions(+), 13 deletions(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=170935"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccComputeInstanceTemplate_resourcePolicies|TestAccPrivatecaCertificateAuthority_privatecaCertificateAuthorityCmekExample You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=170947"