Break apart AudioCodingModule and AcmReceiver

This change makes AudioCodingModule a pure sender and AcmReceiver a pure
receiver.

The Config struct is in practice no longer used by AudioCodingModule,
so a new definition is included in AcmReceiver. The old definition
remains in AudioCodingModule while downstream clients are being
updated.

Bug: webrtc:14867
Change-Id: If0d0b4214c5aa278cf6c85c5b62c6da644de20e0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/291533
Reviewed-by: Tomas Lundqvist <tomasl@google.com>
Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
Reviewed-by: Jakob Ivarsson‎ <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39244}
diff --git a/modules/audio_coding/acm2/acm_send_test.cc b/modules/audio_coding/acm2/acm_send_test.cc
index 3e65f94..fddaa87 100644
--- a/modules/audio_coding/acm2/acm_send_test.cc
+++ b/modules/audio_coding/acm2/acm_send_test.cc
@@ -32,12 +32,7 @@
                                      int source_rate_hz,
                                      int test_duration_ms)
     : clock_(0),
-      acm_(webrtc::AudioCodingModule::Create([this] {
-        AudioCodingModule::Config config;
-        config.clock = &clock_;
-        config.decoder_factory = CreateBuiltinAudioDecoderFactory();
-        return config;
-      }())),
+      acm_(webrtc::AudioCodingModule::Create()),
       audio_source_(audio_source),
       source_rate_hz_(source_rate_hz),
       input_block_size_samples_(