Move Number into core namespace.

Move the number file into the correct `tint::core` namespace from
`tint`. The types names are added to the fluent_types file in order to
make usage cleaner.

Change-Id: I3d8c1c0b18f646698e8f77213bcd2a273e8657d6
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/146681
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Ben Clayton <bclayton@google.com>
diff --git a/src/tint/lang/core/constant/value_test.cc b/src/tint/lang/core/constant/value_test.cc
index a8f9308..8305ceb 100644
--- a/src/tint/lang/core/constant/value_test.cc
+++ b/src/tint/lang/core/constant/value_test.cc
@@ -20,7 +20,7 @@
 namespace tint::core::constant {
 namespace {
 
-using namespace tint::number_suffixes;  // NOLINT
+using namespace tint::core::number_suffixes;  // NOLINT
 
 using ConstantTest_Value = TestHelper;