packages: remove legacy packages upgrade tests

What

This MR removes scripts and ci jobs associated to the legacy packages.

Now we test our dev packages using the last released packages. This is also implied that it is not possible to upgrade from an older release.

I think the assumption is sound considering the octez release and upgrade policy.

This MR depends on two minor MRs. These are mainly there to make sure the ci jobs do not fail with OOM errors.

Why

How

I've changed some postint/preinst/template scripts. I've mainly removed code associated with the legacy packages ( to fetch and use all configurations files ).

I didn't introduce any new test. However I've modified the upgrade tests to use the latest released octez package.

Manually testing the MR

https://gitlab.com/tezos/tezos/-/pipelines/1802637827 A full pipeline : check the log of the install/upgrade scripts

The reviewer should also test the upgrade manually

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