Namely when the subactor fails to lock the root, in which case we
try to be very verbose about how/what failed in logging as well
as ensure we cancel the employed IPC ctx.
Implement the outer `BaseException` handler to handle both styles,
- match on an eg (or the prior std cancel excs) only raising a lone
sub-exc from for former.
- always `as _req_err:` and assign to a new func-global `req_err`
to enable the above matching.
Other,
- raise `DebugStateError` on `status.subactor_uid != actor_uid`.
- fix a `_repl_fail_report` ref error due to making silly assumptions
about the `_repl_fail_msg` global; now copy from global as default.
- various log-fmt and logic expression styling tweaks.
- ignore `trio.Cancelled` by default in `open_crash_handler()`.
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