src: make `StreamPipe::Unpipe()` more resilient

Clean up `StreamPipe::Unpipe()` to be more resilient against
unexpected exceptions, in particular while executing its
`MakeCallback()` line (which can fail in the presence of
termination exceptions), and clean up the getter/setter part
of the code to match that pattern as well (even though it should
not fail as part of regular operations).

PR-URL: https://github.com/nodejs/node/pull/25716


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>