bridge tests: send bridged assets from random parachain to bridged asset hub

Send bridged WNDs: Penpal Rococo -> AH Rococo -> AH Westend
Send bridged ROCs: Penpal Westend -> AH Westend -> AH Rococo

The tests send both ROCs and WNDs, for each direction the native asset is only
used to pay for the transport fees on the local AssetHub, and are not sent over
the bridge.

Including the native asset won't be necessary anymore once we get #4375.

Signed-off-by: Adrian Catangiu <[email protected]>