libkeyringctl/{keyring,sequoia,util}.py:
As Iterable and Iterator are only used for type hints, switch to using
typing.{Iterable,Iterator} instead of
collections.abc.{Iterable,Iterator} for Python < 3.9.0, as older Python
interpreters will otherwise raise TypeError.
CalledProcessError returns bytes for our invocations, the fix that
decoded bytes of stdout was purely to make the mocked test happy while
breaking the actual usage. Restore the behavior and fix the wrong mocked
data.
This feature allows to import from a piped fd like:
> ./keyringctl import --name foobar <(gpg --export foo@bar)
We achieve this even with hidepid by taking the naive approach of
copying the processes fd source to a tempfile and pass around latter.
