chore: add testnet initialization script

[sander2]

Todo:

• [ ] relay chain setup
• [ ] amm curve pools
• [ ] add interlay support (future pr)
• [ ] (optional) some cleanup

[sander2]

LGTM

Just one question: Are we okay with all constructed markets pointing to kusama/kintsugi related currencies like KSM, KBTC, and KINT even if this is called with with-defaults-of="testnet-interlay" (or parachain-endpoint of interlay testnet)?

Good point, I think I'll leave testnet-interlay for a future pr