Bridge xcm emulator testing improvements

[bkontur]

Based around discussion: https://matrix.to/#/!cZvXHjPZkBNsuesmYv:parity.io/$3Al2tcllemEI4RiNVbFlpkEnJC8Iv-wXD-_rLT0NuXI?via=parity.io&via=web3.foundation&via=matrix.parity.io

Check possibility to extend checks for Bridges xcm emulated tests for asset transfer. E.g. start with 200DOT (or WOC on testsnet), and at the end, check where all those 200DOT where splitted, e.g. AHK fees (plus additional price for delivery) + BHK fees + BHP fees + AHP fees (deposit + block_author/staking_pot received fees). We could check events, accounts directly...

Hints:

• specify some sanity treshold for received amount. E.g. we send 200DOT and target account receives just 180DOT, so is 10% loss ok or not?
• it would be cool to print down "table" with all account and amounts (maybe accounts could be as part of some test expectations), that we could see what happens to initial 200DOT
  • or maybe at least to see, how much fees we paid on every hop
  • maybe very stretch , specify some treshold for every hop
• any other check which make sense

Notes:
We have also unit-tests and zombienet tests, maybe (some of) these checks can be added also there. Investigate what make sense, that we could control everything with tests.