Consolidate NNAPI VTS utility code

This CL does additional NNAPI VTS test cleanup, including consolidating
duplicate functionality. Specifically, this CL:
* consolidates the createPreparedModel function, removing the duplicate
* consolidates the std::out ErrorStatus and DeviceStatus code into Utils
* changes non-null constant pointers to constant references
* removes redudant leading namespace specifiers (V1_0::, ::testing, etc.)
* makes the Valdiation tests free functions
* renames device to kDevice and mTestModel to kTestModel

Bug: N/A
Test: mma
Test: VtsHalNeuralnetworksV1_*TargetTest (with sample-all)
Change-Id: Ic401bb1f1760cc10384ac0d30c0c93409b63a9c7
diff --git a/neuralnetworks/1.1/vts/functional/BasicTests.cpp b/neuralnetworks/1.1/vts/functional/BasicTests.cpp
index c239c51..2791e80 100644
--- a/neuralnetworks/1.1/vts/functional/BasicTests.cpp
+++ b/neuralnetworks/1.1/vts/functional/BasicTests.cpp
@@ -28,7 +28,7 @@
 
 // status test
 TEST_F(NeuralnetworksHidlTest, StatusTest) {
-    Return<DeviceStatus> status = device->getStatus();
+    Return<DeviceStatus> status = kDevice->getStatus();
     ASSERT_TRUE(status.isOk());
     EXPECT_EQ(DeviceStatus::AVAILABLE, static_cast<DeviceStatus>(status));
 }
@@ -36,7 +36,7 @@
 // initialization
 TEST_F(NeuralnetworksHidlTest, GetCapabilitiesTest) {
     Return<void> ret =
-            device->getCapabilities_1_1([](ErrorStatus status, const Capabilities& capabilities) {
+            kDevice->getCapabilities_1_1([](ErrorStatus status, const Capabilities& capabilities) {
                 EXPECT_EQ(ErrorStatus::NONE, status);
                 EXPECT_LT(0.0f, capabilities.float32Performance.execTime);
                 EXPECT_LT(0.0f, capabilities.float32Performance.powerUsage);