Replace rtc::Optional with absl::optional in modules/audio processing

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

This CL generated by running script with parameter 'modules/audio_processing'

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: Id29f8de59dba704787c2c38a3d05c60827c181b0
Reviewed-on: https://webrtc-review.googlesource.com/83982
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23653}
diff --git a/modules/audio_processing/audio_processing_impl.cc b/modules/audio_processing/audio_processing_impl.cc
index 71fefe4..2c36a7c 100644
--- a/modules/audio_processing/audio_processing_impl.cc
+++ b/modules/audio_processing/audio_processing_impl.cc
@@ -1677,15 +1677,15 @@
                Error::kNoError) {
       if (metrics.divergent_filter_fraction != -1.0f) {
         stats.divergent_filter_fraction =
-            rtc::Optional<double>(metrics.divergent_filter_fraction);
+            absl::optional<double>(metrics.divergent_filter_fraction);
       }
       if (metrics.echo_return_loss.instant != -100) {
         stats.echo_return_loss =
-            rtc::Optional<double>(metrics.echo_return_loss.instant);
+            absl::optional<double>(metrics.echo_return_loss.instant);
       }
       if (metrics.echo_return_loss_enhancement.instant != -100) {
-        stats.echo_return_loss_enhancement =
-            rtc::Optional<double>(metrics.echo_return_loss_enhancement.instant);
+        stats.echo_return_loss_enhancement = absl::optional<double>(
+            metrics.echo_return_loss_enhancement.instant);
       }
     }
     if (config_.residual_echo_detector.enabled) {
@@ -1702,10 +1702,10 @@
             &delay_median, &delay_std, &fraction_poor_delays) ==
         Error::kNoError) {
       if (delay_median >= 0) {
-        stats.delay_median_ms = rtc::Optional<int32_t>(delay_median);
+        stats.delay_median_ms = absl::optional<int32_t>(delay_median);
       }
       if (delay_std >= 0) {
-        stats.delay_standard_deviation_ms = rtc::Optional<int32_t>(delay_std);
+        stats.delay_standard_deviation_ms = absl::optional<int32_t>(delay_std);
       }
     }
   }