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/offchain/Cargo.toml

@@ -35,7 +35,7 @@ client-db = { package = "substrate-client-db", path = "../db/", default-features
 env_logger = "0.7.0"
 test-client = { package = "substrate-test-runtime-client", path = "../../test/utils/runtime/client" }
 tokio = "0.1.22"
-transaction_pool = { package = "substrate-transaction-pool", path = "../transaction-pool" }
+transaction_pool = { package = "sc-transaction-pool", path = "../../client/transaction-pool" }
 
 [features]
 default = []