Since we can CPFP, we don't have to track the feerate as closely. But
it still needs to get in the mempool, so we use 10 sat/byte, or the
100 block estimate if that is higher.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: `feerates` has new fields `unilateral_anchor_close` to show the feerate used for anchor channels (currently experimental), and `unilateral_close_nonanchor_satoshis`.
Changelog-Changed: JSON-RPC: `feerates` `unilateral_close_satoshis` now assumes anchor channels if enabled (currently experimental).