t/.../critic.t: Fix typo in path name

Signed-off-by: Niels Thykier <niels@thykier.net>
checks/*: use autodie + replace bareword file handles

Signed-off-by: Niels Thykier <niels@thykier.net>
checks/*: Replace all remaining bareword file handles

On top of that, enable the perlcritic policy
InputOutput::ProhibitBarewordFileHandles.

Signed-off-by: Niels Thykier <niels@thykier.net>