Move scalar types over to type/ folder.

This CL moves Bool, F16, F32, I32, U32, and Void over to the type folder
and updates namespaces as needed.

Bug: tint:1718
Change-Id: If3056521e5283ac2d9e1fd09c6daf0f647dd3846
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/113342
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>

src/tint/program_builder.h

diff --git a/src/tint/program_builder.h b/src/tint/program_builder.h
index 5f45e2c..4312528 100644
--- a/src/tint/program_builder.h
+++ b/src/tint/program_builder.h
@@ -92,22 +92,22 @@
 #include "src/tint/program_id.h"
 #include "src/tint/sem/array.h"
 #include "src/tint/sem/array_count.h"
-#include "src/tint/sem/bool.h"
 #include "src/tint/sem/constant.h"
-#include "src/tint/sem/f16.h"
-#include "src/tint/sem/f32.h"
-#include "src/tint/sem/i32.h"
 #include "src/tint/sem/matrix.h"
 #include "src/tint/sem/pointer.h"
 #include "src/tint/sem/struct.h"
-#include "src/tint/sem/u32.h"
 #include "src/tint/sem/vector.h"
-#include "src/tint/sem/void.h"
+#include "src/tint/type/bool.h"
 #include "src/tint/type/depth_texture.h"
 #include "src/tint/type/external_texture.h"
+#include "src/tint/type/f16.h"
+#include "src/tint/type/f32.h"
+#include "src/tint/type/i32.h"
 #include "src/tint/type/multisampled_texture.h"
 #include "src/tint/type/sampled_texture.h"
 #include "src/tint/type/storage_texture.h"
+#include "src/tint/type/u32.h"
+#include "src/tint/type/void.h"
 
 #ifdef CURRENTLY_IN_TINT_PUBLIC_HEADER
 #error "internal tint header being #included from tint.h"