Deleting an existing detector and adding a new detector in local config should delete the existing detector in SFx

[venky526]

Scenario:

1. Created a new detector along with a Dashboard.
2. Changed that detector to a different one and ran a dashboard update.

User expectation: New detector will be created and the old one will be deleted as it happens with our dashboards and charts. Actual result: The new detector is created but the old one still stays.

We need to change this behavior to mirror what we do with dashboards and charts. This can be done by following a similar process like this