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/finality-grandpa/src/tests.rs

@@ -26,7 +26,7 @@ use futures03::{StreamExt as _, TryStreamExt as _};
 use tokio::runtime::current_thread;
 use keyring::Ed25519Keyring;
 use client::LongestChain;
-use client_api::error::Result;
+use sp_blockchain::Result;
 use sr_api::{Core, RuntimeVersion, ApiExt, StorageProof};
 use test_client::{self, runtime::BlockNumber};
 use consensus_common::{BlockOrigin, ForkChoiceStrategy, ImportedAux, BlockImportParams, ImportResult};
@@ -242,7 +242,7 @@ impl Core<Block> for RuntimeApi {
 }
 
 impl ApiExt<Block> for RuntimeApi {
-	type Error = client_api::error::Error;
+	type Error = sp_blockchain::Error;
 
 	fn map_api_result<F: FnOnce(&Self) -> result::Result<R, E>, R, E>(
 		&self,