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
Merged-In: Ic401bb1f1760cc10384ac0d30c0c93409b63a9c7
(cherry picked from commit e16af0a44ba9b76667a598b10a085f808efb8c7c)
diff --git a/neuralnetworks/1.2/vts/functional/ValidateRequest.cpp b/neuralnetworks/1.2/vts/functional/ValidateRequest.cpp
index 684b433..5c52de5 100644
--- a/neuralnetworks/1.2/vts/functional/ValidateRequest.cpp
+++ b/neuralnetworks/1.2/vts/functional/ValidateRequest.cpp
@@ -148,14 +148,12 @@
 
 ///////////////////////////// ENTRY POINT //////////////////////////////////
 
-void ValidationTest::validateRequest(const sp<IPreparedModel>& preparedModel,
-                                     const Request& request) {
+void validateRequest(const sp<IPreparedModel>& preparedModel, const Request& request) {
     removeInputTest(preparedModel, request);
     removeOutputTest(preparedModel, request);
 }
 
-void ValidationTest::validateRequestFailure(const sp<IPreparedModel>& preparedModel,
-                                            const Request& request) {
+void validateRequestFailure(const sp<IPreparedModel>& preparedModel, const Request& request) {
     SCOPED_TRACE("Expecting request to fail [executeSynchronously]");
     Return<void> executeStatus = preparedModel->executeSynchronously(
             request, MeasureTiming::NO,