wifi metrics(proto): Add scan throttling metrics

Bug: 76429171
Test: Unit tests
Change-Id: I77cd03d323e1edbb93369945532c8d2f24bffd68
diff --git a/proto/src/wifi.proto b/proto/src/wifi.proto
index 1605252..934ad88 100644
--- a/proto/src/wifi.proto
+++ b/proto/src/wifi.proto
@@ -413,6 +413,15 @@
 
   // Indicates the number of times we got an interface down in softap mode.
   optional int32 num_soft_ap_interface_down = 103;
+
+  // Indicates the number of scan requests from external apps.
+  optional int32 num_external_app_oneshot_scan_requests = 104;
+
+  // Indicates the number of times a scan request from an external foreground app was throttled.
+  optional int32 num_external_foreground_app_oneshot_scan_requests_throttled = 105;
+
+  // Indicates the number of times a scan request from an external background app was throttled.
+  optional int32 num_external_background_app_oneshot_scan_requests_throttled = 106;
 }
 
 // Information that gets logged for every WiFi connection.