Emit switch statements.

This CL updates the WGSL generator to output switch statements.

Bug: tint:4
Change-Id: I4450b10932960691c76e76869105ade01fdd5a79
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17282
Reviewed-by: David Neto <dneto@google.com>
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 1ed767f..e7ae9cf 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -424,6 +424,7 @@
     writer/wgsl/generator_impl_regardless_test.cc
     writer/wgsl/generator_impl_relational_test.cc
     writer/wgsl/generator_impl_return_test.cc
+    writer/wgsl/generator_impl_switch_test.cc
     writer/wgsl/generator_impl_type_test.cc
     writer/wgsl/generator_impl_unary_derivative_test.cc
     writer/wgsl/generator_impl_unary_method_test.cc