Remove client.backend (#2960)

* generalize tree_root to remove client.backend dependency

* replace client.backend.blockchain.header with client.header

* move used_state_cache_size into client info

* Create intermediate Setup State. Fixes #1134

* remove client.backend from finality proof

* update node-template

* move memory backend into test helper mode

* move test helper into client

* starting the big refactor, remove unused functions

* apply_finality

* apply_finality

* replacing more .backend from environment with client directly

* remove .backend from grandpa by using traits

* remove .backend from babe

* remove .backend from tests where it is not needed

* remove .backend from tests

* fixing tests

* fixing tests

* fixing more tests

* fixing tests

* fix all forks test

* fix style

* fixing unnecessary allocation

* remove old test.

* fix service docs

* apply suggestion

* minor clean ups

* turns out the test-helper features actually is being used!

* fixing line length.

* fix line length

* minor cleaning

* Apply suggestions from code review

thanks, @Basti

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* address grumbles

* simplify finalize block on client

* move block back into inner function

* Apply suggestions from code review

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* use as.ref instead of match

* Update core/client/src/backend.rs

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

substrate/core/cli/src/informant.rs

@@ -16,7 +16,7 @@
 
 //! Console informant. Prints sync progress and block events. Runs on the calling thread.
 
-use client::{backend::Backend, BlockchainEvents};
+use client::BlockchainEvents;
 use futures::{Future, Stream};
 use futures03::{StreamExt as _, TryStreamExt as _};
 use log::{info, warn};
@@ -48,8 +48,8 @@ pub fn build(service: &impl AbstractService) -> impl Future<Item = (), Error = (
 		if let Some((ref last_num, ref last_hash)) = last_best {
 			if n.header.parent_hash() != last_hash && n.is_new_best  {
 				let tree_route = ::client::blockchain::tree_route(
-					#[allow(deprecated)]
-					client.backend().blockchain(),
+					|id| client.header(&id)?.ok_or_else(
+						|| client::error::Error::UnknownBlock(format!("{:?}", id))),
 					BlockId::Hash(last_hash.clone()),
 					BlockId::Hash(n.hash),
 				);