Obviously we can't deterministic-ally call `.load_ref()` (since you'd
have to point to an `id()` or something and presume a particular
py-runtime + virt-mem space for it to exist?) but it at least helps with
the `str` formatting for logging purposes (like `._cancel_rpc_tasks()`)
when `repr`-ing ctxs and their specific "rpc signatures".
Maybe in the future getting this working at least for singleton types
per process (like `Actor` XD ) will be a thing we can support and make
some sense of.. Bo
Originally designed and used throughout `piker`, the subtype adds some
handy pprinting and field diffing extras often handy when viewing struct
types in logging or REPL console interfaces B)
Obvi this rejigs the `tractor.msg` mod into a sub-pkg and moves the
existing namespace obj-pointer stuff into a new `.msg.ptr` sub mod.