automatic upgrade tests for debian packages

What

This MR adds upgrade test for debian packages from "current" to next" and future releases for the octez-node and octez-baker

Why

It's important the transition is smooth and the upgrade tests are integrated in the CI.

How

We add an upgrade test script ( that might might also add as part of the documentation in a different MR ). We also modify the postinst scripts of next packages to handle the upgrade smoothly. The tests only check if the packages can correctly be upgraded, but because the CI runs on docker images we cannot test the scripts that handle the "stop" of the old service and "start" of the new service. These test must be done offline or setting up a VM.

Manually testing the MR

check if the CI job testing the upgrade of the packages runs smoothly and all packages are upgraded correctly.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR