* Change `UnpackError` with `UnpackDefect`
The deprecation warning for `UnpackError` exception raised by some
`inline` procedures in the Nim standard library propagates to the user
code. If the user code has a requirement for building without warnings
this is a problem for the successful execution of the tests. In order
to resolve this, all occurrences of `UnpackError` in the Nim code base
are changed to `UnpackDefect`. Only the type alias is retained to not
break other people's user code since `UnpackError` is exported type.
* Remove the catching of `UnpackDefect`
Defect exceptions should not be cached, because they indicate problem in
the API usage. The code in `nimblesocket.nim` is rewritten to first
check whether there is a value set into the `knownDomain` variable from
the `Option` type before usage.
cc65ae6011