Rename mipLevel to levelCount in TextureDescriptor

This patch renames the field "mipLevel" of TextureDescriptor to
"levelCount" to align with the WebGPU idl.

BUG=dawn:16

Change-Id: I36b30d78831786e4c21ffd641f820375e95a1be5
Reviewed-on: https://dawn-review.googlesource.com/c/2100
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/examples/SampleUtils.cpp b/examples/SampleUtils.cpp
index b2edd4d..0c01964 100644
--- a/examples/SampleUtils.cpp
+++ b/examples/SampleUtils.cpp
@@ -143,7 +143,7 @@
     descriptor.size.depth = 1;
     descriptor.arrayLayer = 1;
     descriptor.format = dawn::TextureFormat::D32FloatS8Uint;
-    descriptor.mipLevel = 1;
+    descriptor.levelCount = 1;
     descriptor.usage = dawn::TextureUsageBit::OutputAttachment;
     auto depthStencilTexture = device.CreateTexture(&descriptor);
     return depthStencilTexture.CreateDefaultTextureView();