Update dependencies

[JanneKiiskila]

• Python 3.8 as minimum (3.5 is EOL already long ago).
• Requests to 2.32.3 to match manifest-tool.
• Pytest 7.4.4 to also match manifest-tool.
• Manifest-tool itself to be 2.6.2 (as that matches the requests).
• Use the git config actions & add cleanup to MCCE-Test-Linux (and add manual dispatch).

We should be aligned with some of the versions, so that we could use the tooling with ONE venv, rather than many.