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/call/BUILD.gn b/call/BUILD.gn
index d994edd..ff72fd9 100644
--- a/call/BUILD.gn
+++ b/call/BUILD.gn
@@ -33,7 +33,6 @@
     "../:typedefs",
     "../api:fec_controller_api",
     "../api:libjingle_peerconnection_api",
-    "../api:optional",
     "../api:transport_api",
     "../api/audio:audio_mixer_api",
     "../api/audio_codecs:audio_codecs_api",
@@ -44,6 +43,7 @@
     "../rtc_base:audio_format_to_string",
     "../rtc_base:rtc_base",
     "../rtc_base:rtc_base_approved",
+    "//third_party/abseil-cpp/absl/types:optional",
   ]
 }
 
@@ -61,9 +61,9 @@
   ]
   deps = [
     "../api:array_view",
-    "../api:optional",
     "../api/transport:bitrate_settings",
     "../rtc_base:rtc_base_approved",
+    "//third_party/abseil-cpp/absl/types:optional",
   ]
 }
 
@@ -87,11 +87,11 @@
     "..:webrtc_common",
     "../api:array_view",
     "../api:libjingle_peerconnection_api",
-    "../api:optional",
     "../modules/rtp_rtcp",
     "../modules/rtp_rtcp:rtp_rtcp_format",
     "../rtc_base:checks",
     "../rtc_base:rtc_base_approved",
+    "//third_party/abseil-cpp/absl/types:optional",
   ]
 }
 
@@ -177,7 +177,6 @@
     ":video_stream_api",
     "..:webrtc_common",
     "../api:callfactory_api",
-    "../api:optional",
     "../api:transport_api",
     "../api/transport:network_control",
     "../audio",
@@ -204,6 +203,7 @@
     "../system_wrappers:field_trial_api",
     "../system_wrappers:metrics_api",
     "../video",
+    "//third_party/abseil-cpp/absl/types:optional",
   ]
 }
 
@@ -220,7 +220,6 @@
     "../:typedefs",
     "../:webrtc_common",
     "../api:libjingle_peerconnection_api",
-    "../api:optional",
     "../api:transport_api",
     "../api/video:video_frame",
     "../api/video_codecs:video_codecs_api",
@@ -228,6 +227,7 @@
     "../modules/rtp_rtcp:rtp_rtcp_format",
     "../rtc_base:checks",
     "../rtc_base:rtc_base_approved",
+    "//third_party/abseil-cpp/absl/types:optional",
   ]
 }