Revert "Make SyncIDs a packed type."

This reverts commit 9de913077a.

Reason for revert: Fails win-trace, somewhat flakily.

Original change's description:
> Make SyncIDs a packed type.
>
> This prepares syncs to use a simple resource map like other
> types, which will make life easier in the trace interpreter.
>
> Bug: angleproject:7775
> Change-Id: Ic2867f6133256f5ce2320eb2b322c1059266b201
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4103720
> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
> Commit-Queue: Jamie Madill <jmadill@chromium.org>
> Reviewed-by: Cody Northrop <cnorthrop@google.com>

Bug: angleproject:7775
Change-Id: I29534b14c973fa34a4cb7457d534cd6156f33cd2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4178010
Auto-Submit: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>

scripts/code_generation_hashes/GLenum_value_to_string_map.json

@@ -1,12 +1,12 @@
 {
   "scripts/gen_gl_enum_utils.py":
-    "3bab69a4a3555ab1551a6e5008534cec",
+    "9663ad2fbaec42c7d3e83f440b0fee67",
   "scripts/gl_angle_ext.xml":
     "e42890bf014f4d4b7ebc07112bbb9764",
   "scripts/registry_xml.py":
     "3d4835d0da60f1d8b76a8ab14f791e31",
   "src/common/gl_enum_utils_autogen.cpp":
-    "fd5198762b90cadf7e682ffb89ae379c",
+    "111b8ace7e690611d3b72ae525729809",
   "src/common/gl_enum_utils_autogen.h":
     "85dea9edf87ad08c322868823e61a40c",
   "third_party/OpenGL-Registry/src/xml/gl.xml":