[functional testing] Support tor-browser-selenium tests against app-staging in CI

[conorsch]

Description

The tor-browser-selenium epic (#3659) tracks work enabling the functional test suite to target "remote" servers, rather than executing Selenium within the app-staging VM. Once the test suite stabilizes in the tbb-0.9.0 branch, we should modify the CI logic for the staging environment to use the new external test client. A brief outline of the work entails:

• Remove Ansible logic installing test dependencies in app-staging from install_files/ansible-base/roles/app-test - [functional testing] Remove TBB install logic from app-test role #3678
• Modify or remove molecule/aws/side_effect.yml to run the new functional test suite logic, including user creation as implemented via Adds --staging flag create-dev-data.py for tests #3672.
• Ensure external client test logic works well in local staging, as well as CI

As we get closer to targeting this work, the outline above may change. Discuss often during team meetings to keep the outline above an accurate depiction of the planned work.

User Stories

As a developer, I want CI to take over as much of the human-driven interaction testing as possible.

As a maintainer, I recognize that substantial changes to testing logic will require corresponding updates to our CI framework.