enc stat: Add Encoding Statistics keys to Codec2 layer

Codec2 layer does not know about the feature of 'EncodingStatitics',
and only knows about each individual statistics, i.e. average_qp,
picture_type.

Bug: 205793764
Bug: 203696003
Test: cts
Change-Id: Ief16ee5499fa11f788dfb73590ba4ac756376dd3
diff --git a/media/codec2/core/include/C2Config.h b/media/codec2/core/include/C2Config.h
index feaa98c..4b96956 100644
--- a/media/codec2/core/include/C2Config.h
+++ b/media/codec2/core/include/C2Config.h
@@ -270,6 +270,9 @@
 
     // encoding quality requirements
     kParamIndexEncodingQualityLevel, // encoders, enum
+
+    // encoding statistics, average block qp of a frame
+    kParamIndexAverageBlockQuantization, // int32
 };
 
 }
@@ -2411,6 +2414,17 @@
     S_HANDHELD = 1              // corresponds to VMAF=70
 );
 
+/**
+ * Video Encoding Statistics Export
+ */
+
+/**
+ * Average block QP exported from video encoder.
+ */
+typedef C2StreamParam<C2Info, C2SimpleValueStruct<int32_t>, kParamIndexAverageBlockQuantization>
+        C2AndroidStreamAverageBlockQuantizationInfo;
+constexpr char C2_PARAMKEY_AVERAGE_QP[] = "coded.average-qp";
+
 /// @}
 
 #endif  // C2CONFIG_H_