[Feature] Disable unstable spec tests in GH actions

[svteb]

Is your feature request related to a problem? Please describe.
Certain tests have been deemed exceptionally unstable and should be refactored in the future. For the purposes of speeding up the development process (reducing re-runs) these should be temporarily disable in GH actions.

• shared_database2 (potentially also shared_database)
• sig_term
• 5g (already resolved)

Describe the solution you'd like
Before proceeding please verify if there are any other tests that could be considered too unstable and mention them in the issue so we can discuss, I am not sure if this data is readily available.

Skip the tags in GH actions until the tests are changed.

Additional context
This change should be reversed in the future in incremental steps.

[martin-mat]

sigterm is an essential test, should be kept in GH actions.