This commit introduces a new `InputLoader` policy by which, if no
input is provided, we use a static default input list.
We also modify the code to use this policy for dnscheck and
stunreachability, with proper input.
We also modify `miniooni` to pass the new `ExperimentName` field to
the `InputLoader` to indicate which default input list to use.
This diff is part of a set of diffs aiming at fixing
https://github.com/ooni/probe/issues/1814 and has been
extracted from https://github.com/ooni/probe-cli/pull/539.
What remains to be done, after this diff has landed is to ensure
things also work for ooniprobe and oonimkall.
2044b78a5a