Use fee estimator to show estimated fee on spend confirm screen

The Issue

If a user tries to send their entire LBC balance to an address (not taking into account tx fees), they are presented with the "get credits" modal and the LBC is not sent. We should mention that transaction fees are associated with sending credits. I'm not sure if we have a way to estimate what those fees are right now (it depends on how many UTXOs are part of of the tx), but we should at least have a better message.

Once we do have the fees, we should have a button called "send max" which takes into account the tx fees.

Steps to reproduce

1. Send entire LBC balance
2. Get message about credits

System Configuration

• LBRY Daemon version: 0.18.0
• LBRY App version: 0.19.2
• LBRY Installation ID:
• Operating system:

Anything Else

Screenshots