Fix swap BTC selection unit tests

[newmattock]

Summary

• wait for the first wallet refresh before selecting a quote so tests do not race the initial zero-balance watch value
• only request a deposit address when the swap actually needs to wait for a deposit
• carry through the explicit max_giveable spending fee and update swap binary tests to assert that fee contract
• make deposit-wait tests deterministic with paused Tokio time

Refs #724.

Testing

• cargo fmt --package swap
• cargo fmt --package swap -- --check
• git diff --check
• cargo test -p swap --bin swap --no-fail-fast