libbinder: make ParcelableHolder moveable

The default impl is enough but previously move ctor was hidden because
of copy ctor.

Without move constructor, ParcelableHolder makes AIDL-generated C++ code
invalid (compilation error) when used with ParcelFileDescriptor (which
is moveable but not copyable intentionally).

Bug: 192197147
Test: m test-piece-6-cpp test-piece-6-ndk
Change-Id: I7154b4960595ee046167fffdd9da2f485b97da0a