Deduplicate pallet call structs used for indirect runtime calls (#1744)

* Small changes

* Define generic bridge pallets call structs

* polkadot-core SignedExtension simplifications

- we don't seem to need to pass the Call as a generic param
- we can use codec(skip) instead of implementing Encode and Decode

* Split BridgeHubRococo and BridgeHubWococo calls

* code review fixes

bridges/primitives/chain-bridge-hub-rococo/Cargo.toml

@@ -7,8 +7,6 @@ edition = "2021"
 license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
 
 [dependencies]
-smallvec = "1.10.0"
-
 # Bridge Dependencies
 
 bp-bridge-hub-cumulus = { path = "../chain-bridge-hub-cumulus", default-features = false }