Add enum for parameter usages.

Currently the ParameterUsages is built entirely from core.def. There are
usages we'd like to use which appear in alternate def files. This Cl
adds a `usages` enum into core.def which allows adding extra usages
above what already appears in core.def

Change-Id: Ibfbdead7a4e875fedce31546f8c1b519efa005f9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/197216
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>
diff --git a/src/tint/lang/core/parameter_usage.h b/src/tint/lang/core/parameter_usage.h
index 10eecf6..5d16272 100644
--- a/src/tint/lang/core/parameter_usage.h
+++ b/src/tint/lang/core/parameter_usage.h
@@ -53,16 +53,22 @@
     kCoords,
     kDdx,
     kDdy,
+    kDepth,
     kDepthRef,
+    kElements,
+    kHeight,
     kInputAttachment,
     kLevel,
+    kNumLevels,
     kOffset,
     kSampleIndex,
     kSampler,
+    kSamples,
     kSourceLaneIndex,
     kTexture,
     kValue,
     kW,
+    kWidth,
     kX,
     kXy,
     kXyz,