Replace curl with gcloud commands in GAM integration

What does this MR do and why?

Replace curl with gcloud commands in GAM integration

Include Workload Identity Federation project number and pool ID in the instructions

EE: true

Changelog: changed

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Context	Before	After
With project ID
Without project ID

Archived

| Context | Before | After | | ------ | ------ | ------ | | With project ID | | | | Without project ID | | |

How to set up and validate locally

1. Simulate a SAAS instance in local GDK

2. In rails console enable the experiment

   Feature.enable(:google_cloud_support_feature_flag)

3. Visit Project > Settings > Integrations > Google Cloud IAM and complete the fields with random values.

4. Visit Project > Settings > Integrations > Google Artifact Registry

5. Confirm that configuration instructions include Workload Identity Federation project number and pool ID from Google Cloud IAM integration

6. Confirm that updating the Project ID form field updates the script.

Related to #460001 (closed)