GLSL: add .expected.glsl files for all tests.

Bug: tint:1301
Change-Id: Id3a591a2fa0dfdb112046d5c57defbae07483e0d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/69480
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>

test/loops/continue_in_switch.wgsl.expected.glsl

@@ -0,0 +1,25 @@
+#version 310 es
+precision mediump float;
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void f() {
+  {
+    for(int i = 0; (i < 4); i = (i + 1)) {
+      switch(i) {
+        case 0: {
+          continue;
+          break;
+        }
+        default: {
+          break;
+        }
+      }
+    }
+  }
+  return;
+}
+void main() {
+  f();
+}
+
+