Add E2E tests for denying via WP Consent API

[tomalec]

Changes proposed in this Pull Request:

This is a small add-on to https://github.com/woocommerce/woocommerce-google-analytics-integration/pull/429. So, we test that a visitor can also deny their consent using the WP Consent API.

Checks:

• [x] Does your code follow the WordPress coding standards?
• [x] Have you written new tests for your changes, as applicable?
• [x] Have you successfully run tests with your changes locally?
• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Screenshots:

Detailed test instructions:

1. Checkout add/wp-consent-api-integration-tests-2 and build extension
2. Setup E2E environment and run tests
3. Confirm all tests pass