Remove simple stringstream usages.

This CL replaces std::o?stringstream with rtc::StringBuilder where that's possible to do without changing any of the surrounding code. It also updates includes and build files as appropriate.

The CL was generated by running 'git grep -l -P std::o?stringstream | xargs perl -pi -e "s/std::o?stringstream/rtc::StringBuilder/g"'. Then I've manually updated the #includes and BUILD files, run 'git cl format' and unstaged any file that would need more complex fixes.

Bug: webrtc:8982
Change-Id: Ibc32153f4a3fd177e260b6ad05ce393972549357
Reviewed-on: https://webrtc-review.googlesource.com/98460
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24605}
diff --git a/modules/audio_coding/test/TestAllCodecs.cc b/modules/audio_coding/test/TestAllCodecs.cc
index 781337c..0099b2a 100644
--- a/modules/audio_coding/test/TestAllCodecs.cc
+++ b/modules/audio_coding/test/TestAllCodecs.cc
@@ -23,6 +23,7 @@
 #include "modules/audio_coding/test/utility.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/stringencode.h"
+#include "rtc_base/strings/string_builder.h"
 #include "test/gtest.h"
 #include "test/testsupport/fileutils.h"
 
@@ -476,7 +477,7 @@
 
 void TestAllCodecs::OpenOutFile(int test_number) {
   std::string filename = webrtc::test::OutputPath();
-  std::ostringstream test_number_str;
+  rtc::StringBuilder test_number_str;
   test_number_str << test_number;
   filename += "testallcodecs_out_";
   filename += test_number_str.str();