Improve local integration testing

[MalinAhlberg]

Please describe the feature
As a developer, I want integration tests to run as fast as possible so that my debugging loop won't take unreasonably much time.

Ideas

• Best way to retest after a change only in the test scripts (assuming all uploaded files etc are unchanged)?
• Best way to retest after having done a small code update in a service?
• Document: how to know when a full rebuild is needed

Acceptance criteria

Additional context
Also see https://github.com/NBISweden/LocalEGA-SE-Deployment/issues/708.

Estimation of size: medium

Estimation of priority: medium