audio: Add IBluetoothA2dp

Similar to IBluetooth interface which controls SCO/HFP,
IBluetoothA2dp controls the A2DP profile. This interface
replaces the following string parameters:

AUDIO_PARAMETER_A2DP_RECONFIG_SUPPORTED
AUDIO_PARAMETER_RECONFIG_A2DP
"A2dpSuspended"

Also, refactor fields used by Module implementation
for persistent child interfaces.

Bug: 270731693
Test: atest VtsHalAudioCoreTargetTest
Change-Id: Ie62952c3bc3af2f53535d716e5b57bf48c661306
diff --git a/audio/aidl/Android.bp b/audio/aidl/Android.bp
index 2c91918..bb48ecd 100644
--- a/audio/aidl/Android.bp
+++ b/audio/aidl/Android.bp
@@ -113,6 +113,7 @@
         "android/hardware/audio/core/AudioPatch.aidl",
         "android/hardware/audio/core/AudioRoute.aidl",
         "android/hardware/audio/core/IBluetooth.aidl",
+        "android/hardware/audio/core/IBluetoothA2dp.aidl",
         "android/hardware/audio/core/IConfig.aidl",
         "android/hardware/audio/core/IModule.aidl",
         "android/hardware/audio/core/IStreamCallback.aidl",