Put HRMP Channel Management on General Admin Track (#7477)

* create ManagerOrigin for HRMP

* missed one

* fix mock

* update GeneralAdmin docs

polkadot/runtime/rococo/src/lib.rs

@@ -1084,6 +1084,7 @@ impl parachains_dmp::Config for Runtime {}
 impl parachains_hrmp::Config for Runtime {
 	type RuntimeOrigin = RuntimeOrigin;
 	type RuntimeEvent = RuntimeEvent;
+	type ChannelManager = EnsureRoot<AccountId>;
 	type Currency = Balances;
 	type WeightInfo = weights::runtime_parachains_hrmp::WeightInfo<Runtime>;
 }