Use absl::make_unique and absl::WrapUnique directly

Instead of going through our wrappers in ptr_util.h.

This CL was generated by the following script:

  git grep -l ptr_util | xargs perl -pi -e 's,#include "rtc_base/ptr_util.h",#include "absl/memory/memory.h",'
  git grep -l MakeUnique | xargs perl -pi -e 's,\b(rtc::)?MakeUnique\b,absl::make_unique,g'
  git grep -l WrapUnique | xargs perl -pi -e 's,\b(rtc::)?WrapUnique\b,absl::WrapUnique,g'
  git checkout -- rtc_base/ptr_util{.h,_unittest.cc}
  git cl format

Followed by manually adding dependencies on
//third_party/abseil-cpp/absl/memory until `gn check` stopped
complaining.

Bug: webrtc:9473
Change-Id: I89ccd363f070479b8c431eb2c3d404a46eaacc1c
Reviewed-on: https://webrtc-review.googlesource.com/86600
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23850}

api/video_codecs/video_encoder_software_fallback_wrapper.cc

@@ -15,12 +15,12 @@
 #include <utility>
 #include <vector>
 
+#include "absl/memory/memory.h"
 #include "media/base/codec.h"
 #include "media/base/h264_profile_level_id.h"
 #include "modules/video_coding/include/video_error_codes.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
-#include "rtc_base/ptr_util.h"
 #include "rtc_base/timeutils.h"
 #include "system_wrappers/include/field_trial.h"
 
@@ -380,7 +380,7 @@ void VideoEncoderSoftwareFallbackWrapper::ValidateSettingsForForcedFallback() {
 std::unique_ptr<VideoEncoder> CreateVideoEncoderSoftwareFallbackWrapper(
     std::unique_ptr<VideoEncoder> sw_fallback_encoder,
     std::unique_ptr<VideoEncoder> hw_encoder) {
-  return rtc::MakeUnique<VideoEncoderSoftwareFallbackWrapper>(
+  return absl::make_unique<VideoEncoderSoftwareFallbackWrapper>(
       std::move(sw_fallback_encoder), std::move(hw_encoder));
 }