Add Labels For Pipelines and ShaderModule for D3D12/Vk

Adds labels for Pipelines and ShaderModule. Includes tests. Backend
functionality is implemented for Pipelines, and completed to best effort
for ShaderModule.

Bug: dawn:840
Change-Id: I55024a83f66d9fc2fc0e8b79e4b9a7ebc6f3cf1c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/62860
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Brandon Jones (Intel) <brandon1.jones@intel.com>
diff --git a/src/dawn_native/ComputePipeline.cpp b/src/dawn_native/ComputePipeline.cpp
index ca173a5..d1a4a8d 100644
--- a/src/dawn_native/ComputePipeline.cpp
+++ b/src/dawn_native/ComputePipeline.cpp
@@ -76,6 +76,7 @@
                                              const ComputePipelineDescriptor* descriptor)
         : PipelineBase(device,
                        descriptor->layout,
+                       descriptor->label,
                        {{SingleShaderStage::Compute, descriptor->compute.module,
                          descriptor->compute.entryPoint}}) {
     }