Reland "Fix collection of audio metrics from PC test framework for audio test"

This is a reland of 2d0880b56954f57548deea51dfa678b80dbf618f

To fix perf bot issue reading of perf results file was updated. Now perf
results file will be generated by each test and then returned via output to
the python script, which will get it and put into final file.

Original change's description:
> Fix collection of audio metrics from PC test framework for audio test
>
> Bug: webrtc:10138
> Change-Id: I18a8509a0cdc4ed1db6894c7540d5c0a155d6233
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/144784
> Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
> Reviewed-by: Oskar Sundbom <ossu@webrtc.org>
> Commit-Queue: Artem Titov <titovartem@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#28514}

Bug: webrtc:10138
Change-Id: I1347f09427736362a2d550612b48e09c06cfb1d1
No-Presubmit: True
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/145201
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Oskar Sundbom <ossu@webrtc.org>
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28527}
diff --git a/audio/BUILD.gn b/audio/BUILD.gn
index 4a3d8fd..0e78a68 100644
--- a/audio/BUILD.gn
+++ b/audio/BUILD.gn
@@ -177,6 +177,7 @@
 
       sources = [
         "test/low_bandwidth_audio_test.cc",
+        "test/low_bandwidth_audio_test_flags.cc",
         "test/pc_low_bandwidth_audio_test.cc",
       ]
 
@@ -192,6 +193,7 @@
         "../rtc_base:rtc_base_approved",
         "../system_wrappers",
         "../test:fileutils",
+        "../test:perf_test",
         "../test:test_common",
         "../test:test_main",
         "../test:test_support",