[xcm-emulator] Chains generic over Network & Integration tests restructure (#2092)

Closes:
- #1383 
- Declared chains can be now be imported and reused in a different
crate.
- Chain declaration are now generic over a generic type `N` (the
Network)
- #1389
- Solved #1383, chains and networks declarations can be restructure to
avoid having to compile all chains when running integrations tests where
are not needed.
- Chains are now declared on its own crate (removed from
`integration-tests-common`)
- Networks are now declared on its own crate (removed from
`integration-tests-common`)
    - Integration tests will import only the relevant Network crate
- `integration-tests-common` is renamed to
`emulated-integration-tests-common`

All this is necessary to be able to implement what is described here:
https://github.com/paritytech/roadmap/issues/56#issuecomment-1777010553

---------

Co-authored-by: command-bot <>

cumulus/parachains/integration-tests/emulated/common/src/xcm_helpers.rs

@@ -13,7 +13,10 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Cumulus
 use parachains_common::AccountId;
+
+// Polkadot
 use xcm::{prelude::*, DoubleEncoded};
 
 /// Helper method to build a XCM with a `Transact` instruction and paying for its execution