cameraservice: Log session index

For tracking camera performance, it is helpful to know the order in
which camera sessions are created.

This CL adds a sessionIndex field to CameraSessionStats which tracks
the order in which sessions were created. This field is logged by
ICameraServiceProxy.

Bug: 236318755
Test: CtsCameraTestCases pass. No functional change.
Change-Id: I392caf8040a8172d0471ce89860a52348188db6a
diff --git a/services/camera/libcameraservice/utils/CameraServiceProxyWrapper.cpp b/services/camera/libcameraservice/utils/CameraServiceProxyWrapper.cpp
index 4225366..af5f3ee 100644
--- a/services/camera/libcameraservice/utils/CameraServiceProxyWrapper.cpp
+++ b/services/camera/libcameraservice/utils/CameraServiceProxyWrapper.cpp
@@ -53,6 +53,7 @@
     mSessionStats.mNewCameraState = CameraSessionStats::CAMERA_STATE_CLOSED;
     mSessionStats.mLatencyMs = latencyMs;
     mSessionStats.mDeviceError = deviceError;
+    mSessionStats.mSessionIndex = 0;
     updateProxyDeviceState(proxyBinder);
 }
 
@@ -74,6 +75,7 @@
 
     mSessionStats.mNewCameraState = CameraSessionStats::CAMERA_STATE_ACTIVE;
     mSessionStats.mMaxPreviewFps = maxPreviewFps;
+    mSessionStats.mSessionIndex++;
     updateProxyDeviceState(proxyBinder);
 
     // Reset mCreationDuration to -1 to distinguish between 1st session