test(ui): add GCP provider support in ProvidersPage tests

[StylusFrost]

Context

This PR implements the critical path of Add GCP provider e2e test flow. PR DEPENDECY #8959

Description

The implementation includes a comprehensive E2E test suite (@PROVIDER-E2E-007) that validates the GCP provider with service account key

@PROVIDER-E2E-007

1. Navigate to providers page
2. Click "Add Provider" button
3. Select GCP provider type
4. Fill provider details (project ID and alias)
5. Select service account credentials type
6. Fill GCP service account key credentials
7. Launch initial scan
8. Verify redirect to provider management page

Steps to review

cd ui
npx playwright test --grep @gcp

Checklist

• Are there new checks included in this PR? No
  • If so, do we need to update permissions for the provider? Please review this carefully.
• Review if the code is being covered by tests.
• Review if code is being documented following this specification https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings
• Review if backport is needed.
• Review if is needed to change the Readme.md
• Ensure new entries are added to CHANGELOG.md, if applicable.

API

• Verify if API specs need to be regenerated.
• Check if version updates are required (e.g., specs, Poetry, etc.).
• Ensure new entries are added to CHANGELOG.md, if applicable.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-actions]

⚠️ Changes detected in the following folders without a corresponding update to the CHANGELOG.md:

• ui

Please add an entry to the corresponding CHANGELOG.md file to maintain a clear history of changes.