demonstration program for multichain settlement workflow

[templexxx]

purpose:

Demonstration of a workflow where more than one Layer 1 chain settles through 'rooch,' with one chain incorporating arbitration functions and another serving solely as a settlement chain.

data flows:

1. l1 msg -> l2
2. l2 msg -> l1

key components: L1/L2 messenger

approach:

Demonstrating, using a simulated Layer 1, how messages are initiated from L1/L2 and precisely transmitted to the target contract on another layer.

[yng17b]

Unit testing can fulfill partial verification tasks: by constructing a bridge through dev_bridge and the client in test_suit, one can assess the deposit and withdrawal operations. @templexxx