"Real world" testing for transaction building and coin selection

[evanlinjin]

Firstly, we need tests to check whether weight calculations are correct for coin selector. I would do this with different descriptors, and attempt to "sign" with "max satisfaction weight".

• Generate a Selection result.
• Construct tx with that result (that is signed).
• Compare weight of final tx with calculations of the CoinSelector::weight* methods.

It will be awesome, if we can pass our raw tx to Bitcoin Core RPC (or something) to verify further.

We also need tests that ensure "minimum drain value" are correct, so that tx will not be rejected for having a dust output.

What other tests do we need?