Rename builtin(sample_mask_{in,out}) to builtin(sample_mask)

Removes the need to pass the storage class to the SPIR-V reader
builtin mapping function.

Added a deprecation warning for sample_mask_{in,out}.

Bug: tint:715
Change-Id: I948ff2de2d5de7bd05e1c6ff45bd721c856900e3
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/47743
Commit-Queue: James Price <jrprice@google.com>
Auto-Submit: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/ast/builtin.cc

@@ -63,6 +63,10 @@ std::ostream& operator<<(std::ostream& out, Builtin builtin) {
       out << "sample_index";
       break;
     }
+    case Builtin::kSampleMask: {
+      out << "sample_mask";
+      break;
+    }
     case Builtin::kSampleMaskIn: {
       out << "sample_mask_in";
       break;

src/ast/builtin.h

@@ -33,8 +33,9 @@ enum class Builtin {
   kLocalInvocationIndex,
   kGlobalInvocationId,
   kSampleIndex,
-  kSampleMaskIn,
-  kSampleMaskOut,
+  kSampleMask,
+  kSampleMaskIn,   // TODO(crbug.com/tint/715): Remove this
+  kSampleMaskOut,  // TODO(crbug.com/tint/715): Remove this
 
   // Below are not currently WGSL builtins, but are included in this enum as
   // they are used by certain backends.