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

This reverts commit e33b0baa088146fc06881387157a92e19fcf5b7b.

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>
diff --git a/test/loops/nested_loops.wgsl.expected.msl b/test/loops/nested_loops.wgsl.expected.msl
index e813828..580263c 100644
--- a/test/loops/nested_loops.wgsl.expected.msl
+++ b/test/loops/nested_loops.wgsl.expected.msl
@@ -5,12 +5,12 @@
   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;
       }