v0.3: from eth to different assets and synthetic stablecoin

This version will require major research because it is not easy task to switch from primitive architecture with one token on all chains from previous versions to a system with multiple assets with changing prices. Add not conversion to stablecoin with exact price but also overcollateralization.

Position management: add different tokens, change messages structure. Maybe add rebalancing. Do we handle price changes onchain or offchain? We already have our datafeeds, can reuse them.

Offchain: switch from de-facto ETH bridging to real collateral abstraction that takes different tokens from one chain and converts to overcollateralized synthetic stablecoin on another. Will need to think about architecture.

Synthetic stablecoin: nothing changes for ERC20 token, it just turns from ETH to USD. Amount to mint/burn is still received from sgx quotes.

https://www.notion.so/Collateral-abstraction-prototypes-versions-1c94460502118020962ecb1423a013ae?pvs=4#1d0446050211806f8c0cd10110436482