Use own middleware to fetch UTXOs

[olszewskimar]

https://aeternity-blockchain.atlassian.net/browse/SW-1331

PR Up: [SW-1331] Use own middleware to retrieve Bitcoin UTXOs by subhod-i · Pull Request #2380 · superhero-com/superhero-wallet

Blocked by “Middleware is still syncing the transactions of testnet accounts, We need to wait till it reaches the tip”. SW-1324: Deploy Bitcore mdw and sync bitcoin mainnet
IN QA

Branch: build/own-middleware