Introduce Device::GetDefaultQueue and deprecate CreateQueue

This makes all backends register the default queue at device
initialization time, so that the same queue is returned by
each call to GetDefaultQueue.

All usages of CreateQueue are replaced by GetDefaultQueue
except a couple ones that could use the queue initialized by
DawnTest::SetUp.

A deprecation warning mechanism is added so that users of Dawn
can now that they should upgrade their usage of the API. It also
comes with a backdoor so we can test that they are emitted.

New DeprecatedAPITests are added that will contain tests for
deprecated APIs, and will also check that deprecation warnings
are produced.

The special casing of GetDefaultQueue in the wire will be done
in a follow-up CL to ease the review. It happens to work through
the regular wire mechanisms at the moment but returns a different
object on each GetDefaultQueue call.

Bug: dawn:22

Change-Id: I78dc1fa474769674278d30040e8d05c658b88360
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/19724
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

examples/CHelloTriangle.cpp

@@ -26,7 +26,7 @@ WGPUTextureFormat swapChainFormat;
 
 void init() {
     device = CreateCppDawnDevice().Release();
-    queue = wgpuDeviceCreateQueue(device);
+    queue = wgpuDeviceGetDefaultQueue(device);
 
     {
         WGPUSwapChainDescriptor descriptor = {};