Modify redirect semantics in preparation for redirect-rule support

[antonok-edm]

Second implementation step of this plan.

When updated DATs are available, begin treating redirects as independent from blocking/exception filters. This means exceptions for blocking should only be looked for in Blocker::exceptions, and exceptions for redirections should only be looked for in Blocker::redirects. Blocker::redirects should be checked for all matches rather than the first match (similar to $csp), and results should be combined accordingly. At this point, a redirection exception should always occur whenever a blocking exception occurs, but the code should be ready to handle the case when they do not occur together.

This will require a minor version bump. Even though there are no breaking interface changes, it is changing the semantics of how BlockerResult::matched and BlockerResult::redirect interact; downstream code will have to be updated accordingly.