AudioFlinger: Add memory leak checking for HAL

$ adb shell setprop libc.debug.malloc.program android.hardware.audio.service
$ adb shell setprop libc.debug.malloc.options backtrace=8
$ adb shell setenforce 0
$ adb shell pkill audioserver
$ adb shell dumpsys media.audio_flinger

Test: Check the audio flinger dumpsys as above.
Bug: 186054996
Bug: 187462632
Change-Id: I610e4b72af9dc1704864adc148e6d6bd23319a8b
(cherry picked from commit 61589a43)
Merged-In: I610e4b72af9dc1704864adc148e6d6bd23319a8b