Revert "Add a per-thread proc table using thread local storage"

This reverts commit b04a92f01b.

Reason for revert: Build failed on win-archive-dbg; see:
https://chromium-review.googlesource.com/c/chromium/src/+/2450792

Original change's description:
> Add a per-thread proc table using thread local storage
>
> In situations where both dawn_wire and dawn_native are used on separate
> threads (Chrome with --single-process or --in-process-gpu), it's
> desirable to have a per-thread proc table so that the WebGPU C++ API can
> still be used. This eliminates classes of bugs with manual
> reference/release errors.
>
> This also changes many of the GetProcs functions to return const
> references to the static proc tables known at compile time, instead of a
> copy.
>
> Bug: none
> Change-Id: I8775bb715b312dd9476a1903fbd797d4b1302614
> Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/29240
> Reviewed-by: Stephen White <senorblanco@chromium.org>
> Reviewed-by: Corentin Wallez <cwallez@chromium.org>
> Commit-Queue: Austin Eng <enga@chromium.org>

TBR=cwallez@chromium.org,senorblanco@chromium.org,enga@chromium.org

Change-Id: I4587b457b7b2dd5d3c7457065bf4e77b95af59d7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: none
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/29442
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>

src/include/dawn_native/DawnNative.h

@@ -170,7 +170,7 @@ namespace dawn_native {
     };
 
     // Backend-agnostic API for dawn_native
-    DAWN_NATIVE_EXPORT const DawnProcTable& GetProcs();
+    DAWN_NATIVE_EXPORT DawnProcTable GetProcs();
 
     // Query the names of all the toggles that are enabled in device
     DAWN_NATIVE_EXPORT std::vector<const char*> GetTogglesUsed(WGPUDevice device);