Adding external context to NucleiEngine

[pedrofialho94]

Please describe your feature request:

Supporting adding an external context to the NucleiEngine to be used when running a scan.

Describe the use case of this feature:

After #5096, it is now possible to cancel a running scan through a context. Adding support for external context would allow a user of the sdk to cancel running scans at any time. This could be used to implement a stop feature in a service that runs nuclei scans.

[tarunKoyalwar]

@pedrofialho94 see #5154