Save Code Now: End to End monitoring

• Select a random, previously successful origin (for all supported origin types)
• Submit via Web and via API
• [... wait for completion ...]

Check completion:

• search origin URL
• check if last visit successful and visit_date >= submit_date
• browse origin (TBD)
• check UI status for save code now request

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Migrated from T2117 (view on Phabricator)