Convert Binder & BinderProxy to NativeAllocationRegistry

Change the Java BinderProxy to only contain a single native pointer,
so that we can get by with a single NativeAllocationRegistry
registration. This adds some indirections and a new allocation. But it
marginally reduces the number of (expensive) JNI field lookups from
native code, and the extra allocation involves significantly less
overhead than registering each object twice. This also cleans up the
code a little by avoiding some explicit reference count adjustments.

Change BinderProxy Binder to use NativeAllocationRegistry instead of
finalize().

Change the mObject field in Binder to hold a non-reference-counted
but owning pointer to JavaBBinderHolder. Have JavaBBinderHolder no
longer inherit from RefBase.

Make it clear that neither Binder.mObject, not BinderProxy.mNativeData
can be null. Remove null checks.

Avoid checking for null returns from C++ new. It would throw
anyway, which would cause the process to abort.

Test: Booted master.

Bug: 65760710

Change-Id: I323d4bdc7e25f8c27b847b6fe2c073eac3f2efe5