rpc: Use the default maxfeerate value as BCH/kB
Summary:
- wallet/rpc: Use the default maxfeerate value as BTC/kB
- test: Add test for default maxfeerate in sendrawtransaction
This patch adds test for the following case
- maxfeerate is omitted, and the actual fee rate is higher than the default value(0.1 BTC/kB)
This is a backport of Core PR16521
Test Plan:
ninja all check-all
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Subscribers: Fabien
Differential Revision: https://reviews.bitcoinabc.org/D8027