feat: display juju debug-log in integration test runs

[PietroPasotti]

Change to _charm-quality-checks.yaml (integration tests part) adding two steps:

for each file found in ./.logs:

1. print to console
2. upload it as artifact

the idea is, we can put our juju debug-log output in there, and the CI will display them and upload as artifact.

Context: https://github.com/canonical/pytest-jubilant/pull/11

Tandem PR to demonstrate the workflow in action: https://github.com/canonical/o11y-tester-operator/actions/runs/16414197049

[lucabello]

To re-review this PR, I would like:

• convert the PR title to conventional commits format, like we practice everywhere
• test the branch with some repository (if you don't know which one, use https://github.com/canonical/o11y-tester-operator) and link a successful run here
• consider updating the diagram here and see how it looks like (adding another box under integration tests maybe)?

[PietroPasotti]

@lucabello ready for another round, all points addressed