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/network/src/chain.rs

@@ -134,8 +134,9 @@ impl<B, E, Block, RA> Client<Block> for SubstrateClient<B, E, Block, RA> where
 		}
 
 		let tree_route = ::client::blockchain::tree_route(
-			#[allow(deprecated)]
-			self.backend().blockchain(),
+			|id| self.header(&id)?.ok_or_else(||
+				client::error::Error::UnknownBlock(format!("{:?}", id))
+			),
 			BlockId::Hash(*block),
 			BlockId::Hash(*base),
 		)?;