[testnet] Add AssetHubRococo <-> AssetHubWestend asset bridging support (#1967)

## Summary

Asset bridging support for AssetHub**Rococo** <-> AssetHub**Wococo** was
added [here](https://github.com/paritytech/polkadot-sdk/pull/1215), so
now we aim to bridge AssetHub**Rococo** and AssetHub**Westend**. (And
perhaps retire AssetHubWococo and the Wococo chains).

## Solution

**bridge-hub-westend-runtime**
- added new runtime as a copy of `bridge-hub-rococo-runtime`
- added support for bridging to `BridgeHubRococo`
- added tests and benchmarks

**bridge-hub-rococo-runtime**
- added support for bridging to `BridgeHubWestend`
- added tests and benchmarks
- internal refactoring by splitting bridge configuration per network,
e.g., `bridge_to_whatevernetwork_config.rs`.

**asset-hub-rococo-runtime**
- added support for asset bridging to `AssetHubWestend` (allows to
receive only WNDs)
- added new xcm router for `Westend`
- added tests and benchmarks

**asset-hub-westend-runtime**
- added support for asset bridging to `AssetHubRococo` (allows to
receive only ROCs)
- added new xcm router for `Rococo`
- added tests and benchmarks

## Deployment

All changes will be deployed as a part of
https://github.com/paritytech/polkadot-sdk/issues/1988.

## TODO

- [x] benchmarks for all pallet instances
- [x] integration tests
- [x] local run scripts


Relates to:
https://github.com/paritytech/parity-bridges-common/issues/2602
Relates to: https://github.com/paritytech/polkadot-sdk/issues/1988

---------

Co-authored-by: command-bot <>
Co-authored-by: Adrian Catangiu <adrian@parity.io>
Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>

bridges/zombienet/README.md

@@ -0,0 +1,31 @@
+# Bridges Tests for Local Rococo <> Wococo Bridge
+
+This folder contains [zombienet](https://github.com/paritytech/zombienet/) based integration tests for both
+onchain and offchain bridges code. Due to some
+[technical diffuculties](https://github.com/paritytech/parity-bridges-common/pull/2649#issue-1965339051), we
+are using native zombienet provider, which means that you need to build some binaries locally.
+
+To start those tests, you need to:
+
+- download latest [zombienet release](https://github.com/paritytech/zombienet/releases);
+
+- build Polkadot binary by running `cargo build -p polkadot --release` command in the
+[`polkadot-sdk`](https://github.com/paritytech/polkadot-sdk) repository clone;
+
+- build Polkadot Parachain binary by running `cargo build -p polkadot-parachain-bin --release` command in the
+[`polkadot-sdk`](https://github.com/paritytech/polkadot-sdk) repository clone;
+
+- ensure that you have [`node`](https://nodejs.org/en) installed. Additionally, we'll need globally installed
+`polkadot/api-cli` package (use `npm install -g @polkadot/api-cli@beta` to install it);
+
+- build Substrate relay by running `cargo build -p substrate-relay --release` command in the
+[`parity-bridges-common`](https://github.com/paritytech/parity-bridges-common) repository clone.
+
+- copy fresh `substrate-relay` binary, built in previous point, to the `~/local_bridge_testing/bin/substrate-relay`;
+
+- change the `POLKADOT_SDK_FOLDER` and `ZOMBIENET_BINARY_PATH` (and ensure that the nearby variables
+have correct values) in the `./run-tests.sh`.
+
+After that, you could run tests with the `./run-tests.sh` command. Hopefully, it'll show the
+"All tests have completed successfully" message in the end. Otherwise, it'll print paths to zombienet
+process logs, which, in turn, may be used to track locations of all spinned relay and parachain nodes.