GpuStats: rename an api and add unit tests

1. insertStats is renamed to insertDriverStats
2. dump all before clear all
3. unit tests have been added

Bug: 141392969
Test: atest gpuservice_unittest
Change-Id: Ifa936bbfd071166a72d1990baf49be0e5ec17fa4
diff --git a/services/gpuservice/TEST_MAPPING b/services/gpuservice/TEST_MAPPING
new file mode 100644
index 0000000..b345355
--- /dev/null
+++ b/services/gpuservice/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "gpuservice_unittest"
+    }
+  ]
+}