* finalization for in_mem
* fetch last finalized block
* pruning: use canonical term instead of final
* finalize blocks in full node
* begin to port light client DB
* add tree-route
* keep number index consistent in full nodes
* fix tests
* disable cache and finish porting light client
* add AsMut to system module
* final leaf is always best
* fix all tests
* Fix comment and trace
* removed unused Into call
* add comment on behavior of `finalize_block`
* move `tree_route` to client common
* tree_route tests
* return slices in TreeRoute
* apply finality up to parent
* add `finalize_block` call
* adjust formatting
* finality notifications and add last finalized block to chain info
* exhaustive match and comments
* fix sync tests by using non-instant finality