tint: fix identity initializer of vec from vec of abstract not remaining abstract

For "vec3(vec3<T>) -> vec3<T>", this CL makes T also include abstract
int and float (all scalars).

Bug: tint:1731
Change-Id: I776c7ba6872c3d680982dbec6b0970389e720611
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/107540
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>

test/tint/bug/tint/1731.wgsl

@@ -0,0 +1,4 @@
+fn g() {
+    const a = vec3(vec3(1, 2, 3));
+    const b = a.x << 40;
+}

test/tint/bug/tint/1731.wgsl.expected.dxc.hlsl

@@ -0,0 +1,7 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+void g() {
+}

test/tint/bug/tint/1731.wgsl.expected.fxc.hlsl

@@ -0,0 +1,7 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+void g() {
+}

test/tint/bug/tint/1731.wgsl.expected.glsl

@@ -0,0 +1,9 @@
+#version 310 es
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void unused_entry_point() {
+  return;
+}
+void g() {
+}
+

test/tint/bug/tint/1731.wgsl.expected.msl

@@ -0,0 +1,6 @@
+#include <metal_stdlib>
+
+using namespace metal;
+void g() {
+}
+

test/tint/bug/tint/1731.wgsl.expected.spvasm

@@ -0,0 +1,21 @@
+; SPIR-V
+; Version: 1.3
+; Generator: Google Tint Compiler; 0
+; Bound: 7
+; Schema: 0
+               OpCapability Shader
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint GLCompute %unused_entry_point "unused_entry_point"
+               OpExecutionMode %unused_entry_point LocalSize 1 1 1
+               OpName %unused_entry_point "unused_entry_point"
+               OpName %g "g"
+       %void = OpTypeVoid
+          %1 = OpTypeFunction %void
+%unused_entry_point = OpFunction %void None %1
+          %4 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %g = OpFunction %void None %1
+          %6 = OpLabel
+               OpReturn
+               OpFunctionEnd

test/tint/bug/tint/1731.wgsl.expected.wgsl

@@ -0,0 +1,4 @@
+fn g() {
+  const a = vec3(vec3(1, 2, 3));
+  const b = (a.x << 40);
+}