Mostly the result of the `RemoteActorError.pformat()` and our
new `_pause/crash_msg: str`s which include the `trio.Task.__repr__()`
in the `log.pdb()` message.
Obvi use the `in_prompt_msg()` to accomplish where not used prior.
ToDo later:
-[ ] still some outstanding questions on how detailed inceptions
should look, eg. in `test_multi_nested_subactors_error_through_nurseries()`
|_maybe we should be more pedantic at checking `.src_uid` vs.
`.relay_uid` fields?
-[ ] staged a placeholder test for verifying correct call-stack frame on
crash handler REPL entry.
-[ ] also need a test to verify that you can't pause from an already paused actor task
such as can happen if you try to step through runtime code that has
a recurrent entry to `._debug.pause()`.
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