dawn.json: Use void* instead of uint8_t* for data pointers

This requires some changes in the wire because WireCmd doesn't know the
size of void. This also adds a handwritten implementation of the Wire
commands for SetSubData that internally converts to uint8_t so that
WireCmd can generate the de/serialization.

BUG=dawn:160

Change-Id: Icbf0fd7dd841639ee6f67333844e027b27a8afcc
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/7780
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>

src/utils/DawnHelpers.cpp

@@ -122,7 +122,7 @@ namespace utils {
         descriptor.usage = usage | dawn::BufferUsageBit::TransferDst;
 
         dawn::Buffer buffer = device.CreateBuffer(&descriptor);
-        buffer.SetSubData(0, size, reinterpret_cast<const uint8_t*>(data));
+        buffer.SetSubData(0, size, data);
         return buffer;
     }