Support USDT/USDC

Allow the user to send and receive stablecoins from their BTC or stable balance.
Let's use this https://docs.flashnet.xyz/products/orchestration/overview
and then maybe add https://docs.garden.finance/ 
I propose to support the following to begin with:
* USDT/USDC Solana
* USDT Tron
* USDT/USDC Ethereum 

If we can generalize, even better. 