Add DiscoveryConfigStatus AWS EC2 resource counters (proto)

This PR adds counters for AWS Instances found/enrolled/failed for a
given DiscoveryConfig and Integration.

api/proto/teleport/discoveryconfig/v1/discoveryconfig.proto

@@ -69,6 +69,9 @@ message DiscoveryConfigStatus {
 
   reserved 5;
   reserved "aws_ec2_instances_discovered";
+
+  // AWSEC2ResourcesDiscovered contains all the AWS EC2 instances discovered.
+  repeated AWSResourcesDiscoveredSummary aws_ec2_resources_discovered = 6;
 }
 
 // DiscoveryConfigState is the state of the discovery config resource.
@@ -83,3 +86,17 @@ enum DiscoveryConfigState {
   // DISCOVERY_CONFIG_STATE_SYNCING is used when the discovery process has started but didn't finished yet.
   DISCOVERY_CONFIG_STATE_SYNCING = 3;
 }
+
+// AWSResourcesDiscoveredSummary represents the AWS resources that were discovered.
+message AWSResourcesDiscoveredSummary {
+  // Integration is the Integration name used to fetch the resource.
+  // Integration is empty if using ambient credentials.
+  string integration = 1;
+  // Found holds the count of resources found.
+  // After a resource is found, it starts the sync process and ends in either an enrolled or a failed resource.
+  uint64 found = 2;
+  // Enrolled holds the count of the resources that were successfully enrolled.
+  uint64 enrolled = 3;
+  // Failed holds the count of the resources that failed to enroll.
+  uint64 failed = 4;
+}