Replace rtc::Optional with absl::optional in audio, call and video

This is a no-op change because rtc::Optional is an alias to absl::optional

This CL generated by running script with parameters 'audio call video':
#!/bin/bash
find $@ -type f \( -name \*.h -o -name \*.cc \) \
-exec sed -i 's|rtc::Optional|absl::optional|g' {} \+ \
-exec sed -i 's|rtc::nullopt|absl::nullopt|g' {} \+ \
-exec sed -i 's|#include "api/optional.h"|#include "absl/types/optional.h"|' {} \+

find $@ -type f -name BUILD.gn \
-exec sed -r -i 's|"(../)*api:optional"|"//third_party/abseil-cpp/absl/types:optional"|' {} \+;

git cl format

Bug: webrtc:9078
Change-Id: I02c5db956846a88a268a300ba086703a02d62e36
Reviewed-on: https://webrtc-review.googlesource.com/83722
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23628}
diff --git a/audio/audio_send_stream_unittest.cc b/audio/audio_send_stream_unittest.cc
index d399120..d0bc45f 100644
--- a/audio/audio_send_stream_unittest.cc
+++ b/audio/audio_send_stream_unittest.cc
@@ -109,17 +109,17 @@
           std::begin(kCodecSpecs), std::end(kCodecSpecs))));
   ON_CALL(*factory.get(), QueryAudioEncoder(_))
       .WillByDefault(Invoke(
-          [](const SdpAudioFormat& format) -> rtc::Optional<AudioCodecInfo> {
+          [](const SdpAudioFormat& format) -> absl::optional<AudioCodecInfo> {
             for (const auto& spec : kCodecSpecs) {
               if (format == spec.format) {
                 return spec.info;
               }
             }
-            return rtc::nullopt;
+            return absl::nullopt;
           }));
   ON_CALL(*factory.get(), MakeAudioEncoderMock(_, _, _, _))
       .WillByDefault(Invoke([](int payload_type, const SdpAudioFormat& format,
-                               rtc::Optional<AudioCodecPairId> codec_pair_id,
+                               absl::optional<AudioCodecPairId> codec_pair_id,
                                std::unique_ptr<AudioEncoder>* return_value) {
         *return_value = SetupAudioEncoderMock(payload_type, format);
       }));
@@ -166,7 +166,7 @@
     return std::unique_ptr<internal::AudioSendStream>(
         new internal::AudioSendStream(
             stream_config_, audio_state_, &worker_queue_, &rtp_transport_,
-            &bitrate_allocator_, &event_log_, &rtcp_rtt_stats_, rtc::nullopt,
+            &bitrate_allocator_, &event_log_, &rtcp_rtt_stats_, absl::nullopt,
             &active_lifetime_,
             std::unique_ptr<voe::ChannelProxy>(channel_proxy_)));
   }
@@ -424,7 +424,7 @@
   EXPECT_CALL(helper.mock_encoder_factory(), MakeAudioEncoderMock(_, _, _, _))
       .WillOnce(Invoke([&kAnaConfigString, &kAnaReconfigString](
                            int payload_type, const SdpAudioFormat& format,
-                           rtc::Optional<AudioCodecPairId> codec_pair_id,
+                           absl::optional<AudioCodecPairId> codec_pair_id,
                            std::unique_ptr<AudioEncoder>* return_value) {
         auto mock_encoder = SetupAudioEncoderMock(payload_type, format);
         EXPECT_CALL(*mock_encoder,