Migrate more tests from Ignore() to phony-assignment

The `Ignore()` intrinsic is about to be deprecated, so don't use it for testing.

Bug: tint:1213
Change-Id: I314ecaeb9a9c337c7b6980189054120a74807ebd
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/67066
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: David Neto <dneto@google.com>
Reviewed-by: James Price <jrprice@google.com>

test/var/initialization/function/array.wgsl

@@ -1,5 +1,5 @@
 [[stage(compute), workgroup_size(1)]]
 fn main() {
     var v : array<i32, 3>;
-    ignore(v);
+    _ = v;
 }

test/var/initialization/function/array.wgsl.expected.hlsl

@@ -1,6 +1,5 @@
 [numthreads(1, 1, 1)]
 void main() {
   int v[3] = (int[3])0;
-  v;
   return;
 }

test/var/initialization/function/array.wgsl.expected.msl

@@ -7,7 +7,6 @@ struct tint_array_wrapper {
 
 kernel void tint_symbol() {
   tint_array_wrapper v = {};
-  (void) v;
   return;
 }
 

test/var/initialization/function/array.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 13
+; Bound: 12
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450

test/var/initialization/function/array.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 [[stage(compute), workgroup_size(1)]]
 fn main() {
   var v : array<i32, 3>;
-  ignore(v);
+  _ = v;
 }

test/var/initialization/function/matrix.wgsl

@@ -1,5 +1,5 @@
 [[stage(compute), workgroup_size(1)]]
 fn main() {
     var v : mat2x3<f32>;
-    ignore(v);
+    _ = v;
 }

test/var/initialization/function/matrix.wgsl.expected.hlsl

@@ -1,6 +1,5 @@
 [numthreads(1, 1, 1)]
 void main() {
   float2x3 v = float2x3(0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f);
-  v;
   return;
 }

test/var/initialization/function/matrix.wgsl.expected.msl

@@ -3,7 +3,6 @@
 using namespace metal;
 kernel void tint_symbol() {
   float2x3 v = float2x3(0.0f);
-  (void) v;
   return;
 }
 

test/var/initialization/function/matrix.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 12
+; Bound: 11
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450

test/var/initialization/function/matrix.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 [[stage(compute), workgroup_size(1)]]
 fn main() {
   var v : mat2x3<f32>;
-  ignore(v);
+  _ = v;
 }

test/var/initialization/function/scalar.wgsl

@@ -1,5 +1,5 @@
 [[stage(compute), workgroup_size(1)]]
 fn main() {
     var v : i32;
-    ignore(v);
+    _ = v;
 }

test/var/initialization/function/scalar.wgsl.expected.hlsl

@@ -1,6 +1,5 @@
 [numthreads(1, 1, 1)]
 void main() {
   int v = 0;
-  v;
   return;
 }

test/var/initialization/function/scalar.wgsl.expected.msl

@@ -3,7 +3,6 @@
 using namespace metal;
 kernel void tint_symbol() {
   int v = 0;
-  (void) v;
   return;
 }
 

test/var/initialization/function/scalar.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 10
+; Bound: 9
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450

test/var/initialization/function/scalar.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 [[stage(compute), workgroup_size(1)]]
 fn main() {
   var v : i32;
-  ignore(v);
+  _ = v;
 }

test/var/initialization/function/struct.wgsl

@@ -6,5 +6,5 @@ struct S {
 [[stage(compute), workgroup_size(1)]]
 fn main() {
     var v : S;
-    ignore(v);
+    _ = v;
 }

test/var/initialization/function/struct.wgsl.expected.hlsl

@@ -6,6 +6,5 @@ struct S {
 [numthreads(1, 1, 1)]
 void main() {
   S v = (S)0;
-  v;
   return;
 }

test/var/initialization/function/struct.wgsl.expected.msl

@@ -8,7 +8,6 @@ struct S {
 
 kernel void tint_symbol() {
   S v = {};
-  (void) v;
   return;
 }
 

test/var/initialization/function/struct.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 12
+; Bound: 11
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450

test/var/initialization/function/struct.wgsl.expected.wgsl

@@ -6,5 +6,5 @@ struct S {
 [[stage(compute), workgroup_size(1)]]
 fn main() {
   var v : S;
-  ignore(v);
+  _ = v;
 }

test/var/initialization/function/vector.wgsl

@@ -1,5 +1,5 @@
 [[stage(compute), workgroup_size(1)]]
 fn main() {
     var v : vec3<i32>;
-    ignore(v);
+    _ = v;
 }

test/var/initialization/function/vector.wgsl.expected.hlsl

@@ -1,6 +1,5 @@
 [numthreads(1, 1, 1)]
 void main() {
   int3 v = int3(0, 0, 0);
-  v;
   return;
 }

test/var/initialization/function/vector.wgsl.expected.msl

@@ -3,7 +3,6 @@
 using namespace metal;
 kernel void tint_symbol() {
   int3 v = 0;
-  (void) v;
   return;
 }
 

test/var/initialization/function/vector.wgsl.expected.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.3
 ; Generator: Google Tint Compiler; 0
-; Bound: 11
+; Bound: 10
 ; Schema: 0
                OpCapability Shader
                OpMemoryModel Logical GLSL450

test/var/initialization/function/vector.wgsl.expected.wgsl

@@ -1,5 +1,5 @@
 [[stage(compute), workgroup_size(1)]]
 fn main() {
   var v : vec3<i32>;
-  ignore(v);
+  _ = v;
 }