Improve UI for Google Cloud runner provisioning

What does this MR do and why?

Depends on !146226 (merged)

Improve UI for Google Cloud runner provisioning

• Add machine type popover link
• Add aria-label for external icons
• Add copy to clipboard button for commands
• Wrap Terraform file name in code span
• Update “Setup instructions” button variant based on state
• Fix form and modal headings
• Fix zone popover link
• Fix text strings with missing period
• Fix color of help icons
• Update modal step 1 text

MR acceptance checklist

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Screenshots or screen recordings

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Before	After

How to set up and validate locally

1. Simulate a SaaS instance in your GDK
2. Enable the feature flag

 echo "Feature.enable(:google_cloud_runner_provisioning)" | rails c

1. Visit project creation views (should not be available on admin and groups for now)
2. Select google cloud radio option (for platform)
3. Create runner
4. New options should show for register view if you chose the google cloud platform option
5. Existing runner options should still show for other platform selections
6. Fill the form values with the following:

    "Google cloud project ID": "dev-gcp-s3c-integrati-9abafed1",
    "region": "us-central1",
    "zone": "us-central1-a",

1. Click the Show instructions button and you should be able to see the instructions