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/expressions/unary/complement/complement.wgsl

@@ -0,0 +1,15 @@
+fn i(x : i32) -> i32 {
+  return ~x;
+}
+
+fn u(x : u32) -> u32 {
+  return ~x;
+}
+
+fn vi(x : vec4<i32>) -> vec4<i32> {
+  return ~x;
+}
+
+fn vu(x : vec4<u32>) -> vec4<u32> {
+  return ~x;
+}