* Make server.prepare idempotent, don't cleanup containers on server.start
* Implement rolling upgrade E2E tests
* Apply Akis' suggestions from code review
* Apply Saturn's suggestions from review
* Communicate RollingRelease on GHA and test automation results channel
* Implement E2E test case versioning for rolling release tests
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Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Akis Maziotis <akis.maziotis@mattermost.com>
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