Removing AudioAllocationSettings moving functionality to AudioSendStream.

This is a no-op change that just removes the AudioAllocationSettings
helper class that was previously introduced since the field trials in it
were used in several places. Those other usages has now been removed
and AudioSendStream is now the only user. By moving the trials directly
to AudioSendStream we reduce the reader overhead when trying to follow
what a particular field trial does.

The "WebRTC-Audio-ForceNoTWCC" trial was removed as it is always set
together with "WebRTC-Audio-ABWENoTWCC".

Bug: webrtc:9883
Change-Id: Ib63589255bfe7adb155ea41279bdcd153f1536c8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/155366
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Oskar Sundbom <ossu@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29371}
diff --git a/audio/BUILD.gn b/audio/BUILD.gn
index fa16bb7..ba4518d 100644
--- a/audio/BUILD.gn
+++ b/audio/BUILD.gn
@@ -82,7 +82,7 @@
     "../rtc_base:rtc_base_approved",
     "../rtc_base:rtc_task_queue",
     "../rtc_base:safe_minmax",
-    "../rtc_base/experiments:audio_allocation_settings",
+    "../rtc_base/experiments:field_trial_parser",
     "../system_wrappers",
     "../system_wrappers:field_trial",
     "../system_wrappers:metrics",