[➕ Feature]: Support deduplication rules for unknown providers

[tuantran0910]

I believe it's beneficial to have this option in case we decide against creating a provider for various reasons and instead opt to use a virtual provider.

For example, in our data system, we have several components like dbt, Jenkins, and others that do not directly send alerts. We send alerts via webhook, designating the source as these components to indicate where the alerts originated.