Add duration to securityTest Model

[J12934]

Is your feature request related to a problem? Please describe.
It is hard to see afterwards how long a scan took.

Describe the solution you'd like
A new attribute on the securityTest Model which has the total securityTest duration in ms or s.

Describe alternatives you've considered
Two attributes start and end time.

Additional context
Would especially help to analyse if the scan performance has improved or degraded over time.