[Analytics] Add proto and enum for establish_connection event.

Set up the proto and enums in advance. No real logic.

LOG_STORAGE_INCREASE(GB/week): 0.5
Based on go/ns-analytics-worksheet

PiperOrigin-RevId: 398810446

proto/sharing_enums.proto

@@ -182,6 +182,9 @@ enum EventType {
 
   // Request setting permissions (Wifi/BT/location/airplane mode).
   REQUEST_SETTING_PERMISSIONS = 47;
+
+  // Set up a connection with the remote device.
+  ESTABLISH_CONNECTION = 48;
 }
 
 // Event category to differentiate whether this comes from sender or receiver,
@@ -218,6 +221,15 @@ enum DataUsage {
   OFFLINE = 3;
 }
 
+// The status of establishing a connection. Used by ESTABLISH_CONNECTION.
+enum EstablishConnectionStatus {
+  CONNECTION_STATUS_UNKNOWN = 0;
+
+  CONNECTION_STATUS_SUCCESS = 1;
+  CONNECTION_STATUS_FAILURE = 2;
+  CONNECTION_STATUS_CANCELLATION = 3;
+}
+
 // The status of sending and receiving attachments. Used by SEND_ATTACHMENTS.
 enum AttachmentTransmissionStatus {
   UNKNOWN_ATTACHMENT_TRANSMISSION_STATUS = 0;