Remove obex library code from frameworks/base.

The obex library has been migrated to platform/external/obex as it uses
the BSD license and should not be in any non-3p repo. Only the ObexPacket
class is retained as it is a public API.

Bug: 219056000
Bug: 220211554
Test: Manual
Change-Id: If279fda41b7790abe0f25d9ebd8ea4c6fb58cbbb