Reset Internal D3D12 Device After Test Shutdown

Adds dawn_native::ResetDeviceInternal, which allows us to destroy and
create a new ID3D12Device. The device should be reset after every test
when GPU-based validation is enabled in order to prevent GBV objects
from using a significant amount of memory over time.

Bug: dawn:623
Change-Id: I654d093d993ab0198c6c240bd0f3f843d2762680
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/41340
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Rafael Cintron <rafael.cintron@microsoft.com>
Commit-Queue: Brandon Jones <brandon1.jones@intel.com>

src/dawn_native/DawnNative.cpp

@@ -111,6 +111,10 @@ namespace dawn_native {
         return reinterpret_cast<WGPUDevice>(mImpl->CreateDevice(deviceDescriptor));
     }
 
+    void Adapter::ResetInternalDeviceForTesting() {
+        mImpl->ResetInternalDeviceForTesting();
+    }
+
     // AdapterDiscoverOptionsBase
 
     AdapterDiscoveryOptionsBase::AdapterDiscoveryOptionsBase(WGPUBackendType type)