Add HAL interface to replace aaudio system property.

Using the HAL interface instead of reading system property is a better
option when moving to AIDL HAL. The replaced property includes:
  - aaudio.mixer_bursts
  - aaudio.hw_burst_min_usec

Test: atest AAudioTests
Bug: 193275465
Change-Id: I9c9a04296e56ff083babcfa089fcdddc6b89ed94
diff --git a/media/libaudioclient/AudioSystem.cpp b/media/libaudioclient/AudioSystem.cpp
index 17557e7..317ad1e 100644
--- a/media/libaudioclient/AudioSystem.cpp
+++ b/media/libaudioclient/AudioSystem.cpp
@@ -2367,6 +2367,22 @@
     return af->getMmapPolicyInfos(policyType, policyInfos);
 }
 
+int32_t AudioSystem::getAAudioMixerBurstCount() {
+    const sp<IAudioFlinger>& af = AudioSystem::get_audio_flinger();
+    if (af == nullptr) {
+        return PERMISSION_DENIED;
+    }
+    return af->getAAudioMixerBurstCount();
+}
+
+int32_t AudioSystem::getAAudioHardwareBurstMinUsec() {
+    const sp<IAudioFlinger>& af = AudioSystem::get_audio_flinger();
+    if (af == nullptr) {
+        return PERMISSION_DENIED;
+    }
+    return af->getAAudioHardwareBurstMinUsec();
+}
+
 // ---------------------------------------------------------------------------
 
 int AudioSystem::AudioPolicyServiceClient::addAudioPortCallback(