Remove/cleanup extrude implementations

[pjenvey]

Now that we do a lot less in middleware (the db transaction handling and precondition checks are no longer middleware), we don't need as many extrude (basically an extract that works in middlewares, operating on ServiceRequest).

They can instead operate on actix's higher level HttpRequest, simplifying some of their implementations. E.g. the x_from_path methods wouldn't need extract path elements as manually as they currently do (requiring them to urldecode)

[jrconlin]

It might(?) be worth converting a few of these to From<T> or similar (e.g HawkIdentifer::from(RequestHead) and feels more rusty. We might even be able to put the rejectua::check(RequestHead) stuff inside the HawkIdentifier code since we already bottleneck there pretty hard.

[ethowitz]

JIRA