Refactor the debian test fixtures building

[pulpbot]

Author: @quba42 (quba42)

Redmine Issue: 7442, https://pulp.plan.io/issues/7442

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The idea is to use best Makefile practices.

Currently, we are building all packages multiple times for each repository.

Instead, packages should have there own make targets which are dependent targets of the repositories that need them.

Ideally all built repositories could share a common pool folder (either directly or using symlinks), so we do not build an unnecessarily large fixtures container.
This might be prohibitively hard to achieve with the current repo building tooling.

[stale]

This issue has been marked 'stale' due to lack of recent activity. If there is no further activity, the issue will be closed in another 30 days. Thank you for your contribution!

[hstct]

Instead of refactoring the Makefile in pulp-fixtures the new goal is provide precompiled local test packages as well as necessary Release and Package files and use pytest fixtures provided by pulp-smash (and later by pulpcore) to create a local test data.

[stale]

This issue is no longer marked for closure.