Feature Request: Add resourceLocation as one of the possible values for ActivityLogAlertLeafCondition

[activityLogAlerts API](https://github.com/Azure/azure-rest-api-specs/blob/master/specification/monitor/resource-manager/Microsoft.Insights/stable/2017-04-01/activityLogAlerts_API.json)

ActivityLogAlertLeafCondition allows for a condition to be specified for an ActivityLog alert.
Currently, only the following values are supported:

> "ActivityLogAlertLeafCondition": {
"properties": {
"field": {
"type": "string",
"description": "The name of the field that this condition will examine. The possible values for this field are (case-insensitive): 'resourceId', 'category', 'caller', 'level', 'operationName', 'resourceGroup', 'resourceProvider', 'status', 'subStatus', 'resourceType', or anything beginning with 'properties.'."
},

Currently, there is no way to filter on the location of the resource.
The specific use-case is to generate region-specific resource alerts and then add them to a service bus queue.
Service bus namespaces are region-specific, so each queue in a particular namespace could store log alerts for resources in its own region.

Thanks,
Sourabh