Restore "MSL writer: make signed int overflow defined behaviour"

This reverts commit e33b0baa08.

Added tests/expressions/literals/intmin.wgsl test.

Bug: tint:124
Change-Id: I3d46f939ff20fa377ddb5fcb52f9afe728b8e430
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/60441
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Reviewed-by: David Neto <dneto@google.com>

test/loops/continue_in_switch.wgsl.expected.msl

@@ -2,7 +2,7 @@
 
 using namespace metal;
 kernel void f() {
-  for(int i = 0; (i < 4); i = (i + 1)) {
+  for(int i = 0; (i < 4); i = as_type<int>((as_type<uint>(i) + as_type<uint>(1)))) {
     switch(i) {
       case 0: {
         continue;

test/loops/loop.wgsl.expected.msl

@@ -4,7 +4,7 @@ using namespace metal;
 int f() {
   int i = 0;
   while (true) {
-    i = (i + 1);
+    i = as_type<int>((as_type<uint>(i) + as_type<uint>(1)));
     if ((i > 4)) {
       return i;
     }

test/loops/loop_with_continuing.wgsl.expected.msl

@@ -8,7 +8,7 @@ int f() {
       return i;
     }
     {
-      i = (i + 1);
+      i = as_type<int>((as_type<uint>(i) + as_type<uint>(1)));
     }
   }
   return 0;

test/loops/nested_loops.wgsl.expected.msl

@@ -5,12 +5,12 @@ int f() {
   int i = 0;
   int j = 0;
   while (true) {
-    i = (i + 1);
+    i = as_type<int>((as_type<uint>(i) + as_type<uint>(1)));
     if ((i > 4)) {
       return 1;
     }
     while (true) {
-      j = (j + 1);
+      j = as_type<int>((as_type<uint>(j) + as_type<uint>(1)));
       if ((j > 4)) {
         return 2;
       }

test/loops/nested_loops_with_continuing.wgsl.expected.msl

@@ -13,11 +13,11 @@ int f() {
         return 2;
       }
       {
-        j = (j + 1);
+        j = as_type<int>((as_type<uint>(j) + as_type<uint>(1)));
       }
     }
     {
-      i = (i + 1);
+      i = as_type<int>((as_type<uint>(i) + as_type<uint>(1)));
     }
   }
   return 0;