bluetooth_manager: Use dumpAsync to not block on Bluetooth

IBinder#dump on a BinderProxy is making a non ONEWAY call and
as result can block the system_server. To avoid this ONEWAY
outgoing calls are prohibited in the system_server.

So IBinder#dump is replaced by IBinder#dumpAsync to dump using a
ONEWAY binder transaction.

The effect of this is that the bluetooth_manager service will not
propagate anymore exception raised by AdapterService#dump to
dumpsys.

This effect is acceptable as the exception will still be reported
to logcat.

Bug: 239890880
Test: m com.android.btservices
Test: `adb shell dumpsys bluetooth_manager` and check the log for
  the absence of warnings from Binder
Test: Modify the Bluetooth app to sleep for 10 seconds then run
  `adb shell dumpsys bluetooth_manager` and confirm that dumpsys
  timeouts
Flag: Exempt, dumpsys is a debug feature + full manual testing was done.
Change-Id: Ia7146349813990405f436743310def117b1d3890