Remove all (non-dev) client references from frame, activate dependency enforcer (#4184)

* Move transaction pool to primitives

* move backend, errors into primitives

* remove unused client depencies

* Move rpc-api into primitives

* Move peerset back to client

* Move rpc/api back to client, move palette/support/rpc into utils

* move support-rpc into subfolder

* move system-rpc into utils

* move transaction-pool  and -graph back into client

* fix broken imports

* Clean up test primitives

* Make support test utils independent of frame

* remove unnecessary node dependencies from service

* Reactivate dependency script:
 - only enforce the now achieved status quo will remain
 - allow for primitives to depend on /client for now without failing
 - more discriptive error message so people understand, what it wants
 - minor fix to differentiative between ../client and /client (which may be a subfolder)
 - don't allow this to fail anylonger.

* fix doc comment

* 'Should not' rather than 'must not'.

* Revert unwanted dependency changes

* fix faulty import

* fixup derive_more version

* fix wrong import path

substrate/client/db/src/cache/list_cache.rs

@@ -43,7 +43,7 @@ use std::collections::{BTreeSet, BTreeMap};
 
 use log::warn;
 
-use client_api::error::{Error as ClientError, Result as ClientResult};
+use sp_blockchain::{Error as ClientError, Result as ClientResult};
 use sr_primitives::traits::{
 	Block as BlockT, NumberFor, Zero, Bounded, CheckedSub
 };