scylla-gdb.py: pointer_metadata: allow constructing from non-seastar pointers
scylla-gdb.py: pointer_metadata: allow constructing from non-seastar pointers

scylladb/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla