AuRa improvements (#8255)

* AuRa improvements

Hot and fresh AuRa improvements. This pr does the following:

- Move code belonging to the import queue etc to import_queue.rs
- Introduce `ImportQueueParams` and `StartAuraParams` structs to make
it more easier to understand what parameters we pass to AuRa.
- Introduce `CheckForEquivocation` to tell AuRa if it should check for
equivocation on block import. This is required for parachains, because
they are allowed to equivocate when they build two blocks for the same
slot, but for different relay chain parents.

* Update client/consensus/aura/src/import_queue.rs

Co-authored-by: André Silva <[email protected]>

* Fix compilation

* AAA

Co-authored-by: André Silva <[email protected]>