OboeTester: handle rerouting in the Error Callback test

Starting from Android 17, a stream on the legacy path may be rerouted
instead of disconnected when a headset is plugged or unplugged. In that
case the error callback never fires and the Error Callback test in
OboeTester never reports PASS.

Register a routing callback (when the platform supports it) and run the
same "delete the callback while it is in use" experiment from
onRoutingChanged(). A routing callback that merely reports the initial
devices is ignored so the test still requires a real plug/unplug event.
cleanup() is serialized with a mutex because both the error callback and
the routing callback may fire for the same event on MMAP streams.

Unexpected (non-disconnect) errors are now reported through a separate
getCallbackError() so the UI can show a clear failure message instead of
a bogus magic value.

Library changes:
- Add virtual destructor to AudioStreamRoutingCallback.
- Add OboeExtensions::isRoutingChangedCallbackSupported().

Bug: 560318727