Replace rtc::Optional with absl::optional in test and rtc_tools

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

This CL generated by running script with parameters 'test rtc_tools'

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: Ibb43c737f4c45fe300736382b0dd2d8ab32c6377
Reviewed-on: https://webrtc-review.googlesource.com/83944
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23642}
diff --git a/test/fuzzers/audio_decoder_fuzzer.cc b/test/fuzzers/audio_decoder_fuzzer.cc
index f6ac4cb..40a7315 100644
--- a/test/fuzzers/audio_decoder_fuzzer.cc
+++ b/test/fuzzers/audio_decoder_fuzzer.cc
@@ -12,8 +12,8 @@
 
 #include <limits>
 
+#include "absl/types/optional.h"
 #include "api/audio_codecs/audio_decoder.h"
-#include "api/optional.h"
 #include "modules/rtp_rtcp/source/byte_io.h"
 #include "rtc_base/checks.h"