Convert most remaining usages to utils::StringStream.

This CL converts most of the remaining Tint usages (leaving out the
fuzzer code and some float_to_string code).

Bug: tint:1686
Change-Id: I4d5cef176c15479250861903870ec5bec0f95b5e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/122002
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/utils/io/tmpfile.h b/src/tint/utils/io/tmpfile.h
index 24e7208..7949a371 100644
--- a/src/tint/utils/io/tmpfile.h
+++ b/src/tint/utils/io/tmpfile.h
@@ -18,6 +18,8 @@
 #include <sstream>
 #include <string>
 
+#include "src/tint/utils/string_stream.h"
+
 namespace tint::utils {
 
 /// TmpFile constructs a temporary file that can be written to, and is
@@ -55,7 +57,7 @@
     /// @return a reference to this TmpFile
     template <typename T>
     inline TmpFile& operator<<(T&& data) {
-        std::stringstream ss;
+        utils::StringStream ss;
         ss << data;
         std::string str = ss.str();
         Append(str.data(), str.size());