ci: Add disallow-legacy-apiary presubmit check to basic-pr-checks

[jcromanu]

Summary

Add an automated disallow-legacy-apiary presubmit job to .github/workflows/basic-pr-checks.yml to prevent PRs from introducing new imports of the legacy Apiary client (google.golang.org/api/compute/*) or calls to deprecated client factories in handwritten overrides and templates.

Release Note Template for Downstream PRs (will be copied)

See Write release notes for guidance.

[github-actions]

Googlers: For automatic test runs see go/terraform-auto-test-runs.

@rileykarson, 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 for commit fb04281:

Diff report

Your PR hasn't generated any diffs, but I'll let you know if a future commit does.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes for commit 30cc11a:

Diff report

Your PR hasn't generated any diffs, but I'll let you know if a future commit does.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes for commit 4f5d4f5:

Diff report

Your PR hasn't generated any diffs, but I'll let you know if a future commit does.

[rileykarson]

Let me know when this is ready for review!

[jcromanu]

@rileykarson , the script is ready , should we wait until the last tickets of the apiary migration are done before merging it?