Add automated release tests for RC and GA builds + include test report

[troglobit]

Description

There's currently a lot of manual overhead verifying release builds. We should add some basic release tests:

1. Standard regression test suite?
2. Additional test or long-runs?
3. Automate GNS3 image validation?

The test report can also be generated from the test results on the git hash that is tagged. This could be a first good step, but does not help with binary validation.

[troglobit]

Reopen due to problems with running regression tests in the release suite. See e496826, for v26.04.0-rc2 for details, or the logs_66949871624.zip directly.

CCB: Decision to reopen and move target milestone.