[FEATURE REQ] Event System topic misses Monitor Alert/Action group as destination.

### API Spec link

https://learn.microsoft.com/en-us/rest/api/eventgrid/controlplane/system-topic-event-subscriptions/create-or-update?view=rest-eventgrid-controlplane-2022-06-15&tabs=HTTP

### API Spec version

2024-06-01-preview, 2022-06-15

### Please describe the feature.

It is not possible to set "monitor alert" for the system topic event types. The event data can be forwarded to an event hub, storage queue etc. However, the monitor alert (or action group) is missing from this list.

https://learn.microsoft.com/en-us/rest/api/eventgrid/controlplane/system-topic-event-subscriptions/create-or-update?view=rest-eventgrid-controlplane-2022-06-15&tabs=HTTP

I'm not really sure if the link for "API Spec link" is the right one. Please correct it in case it is incorrect.

There is an active issue in the Terraform provider which has many 👍 https://github.com/hashicorp/terraform-provider-azurerm/issues/24873

Start with the linked Event Grid create-or-update API specification and compare the documented destination options with the requested Monitor Alert or Action Group destination. Confirm whether the API version supports this capability and define what specification changes would represent it; the issue is complete when the supported destination is accurately modeled and documented.

Written by the indexing model from the issue text.