Run Geo end-to-end tests on staging

Once Geo in enabled on staging, we should regularly run Geo end-to-end tests.

Some considerations:

• This may involve changes to files in multiple projects: gitlab-qa, pipeline-common, staging
• Geo tests require an EE license and secondary node URL. The current Test::Instance::Staging scenario does not support either of those (Test:: Instance::Geo scenario does support those inputs)
• When and how often should Geo end-to-end tests run on staging?
• Is there any additional documentation or demos required to help SETs/Engineers investigate Geo test failures on staging (or in general)?