Apply the retrying logic at each step when following redirects

[aeqz]

Clarification and motivation

After the work done in #250 , we allow to configure Xrefcheck to follow redirects in a rule-based way that is applied through all the links in a redirect chain. However, the retrying logic that we apply when validating external resources is applied to the entire redirect chain and not at each one of its requests.

Acceptance criteria

• The retrying behavior is applied at each request when following redirects, instead of to the entire chain.
• When a redirect is followed, the progress bar handles it in some way that we discuss to be appropriate.