[Bridges] Move chain definitions to separate folder (#3822)

Related to
https://github.com/paritytech/parity-bridges-common/issues/2538

This PR doesn't contain any functional changes. 

The PR moves specific bridged chain definitions from
`bridges/primitives` to `bridges/chains` folder in order to facilitate
the migration of the `parity-bridges-repo` into `polkadot-sdk` as
discussed in https://hackmd.io/LprWjZ0bQXKpFeveYHIRXw?view

Apart from this it also includes some cosmetic changes to some
`Cargo.toml` files as a result of running `diener workspacify`.

cumulus/parachains/integration-tests/emulated/chains/relays/rococo/Cargo.toml

@@ -25,5 +25,5 @@ rococo-runtime-constants = { path = "../../../../../../../polkadot/runtime/rococ
 rococo-runtime = { path = "../../../../../../../polkadot/runtime/rococo" }
 
 # Cumulus
-parachains-common = { path = "../../../../../../parachains/common" }
+parachains-common = { path = "../../../../../common" }
 emulated-integration-tests-common = { path = "../../../common", default-features = false }

cumulus/parachains/integration-tests/emulated/chains/relays/westend/Cargo.toml

@@ -27,5 +27,5 @@ westend-runtime-constants = { path = "../../../../../../../polkadot/runtime/west
 westend-runtime = { path = "../../../../../../../polkadot/runtime/westend" }
 
 # Cumulus
-parachains-common = { path = "../../../../../../parachains/common" }
+parachains-common = { path = "../../../../../common" }
 emulated-integration-tests-common = { path = "../../../common", default-features = false }