Replace config max counterpary dust_limit_satoshis by a constant.

Current Bitcoin Core's policy will reject a p2wsh as a dust if it's
under 330 satoshis. A typical p2wsh output is 43 bytes big to which
Core's `GetDustThreshold()` sums up a minimal spend of 67 bytes (even
if a p2wsh witnessScript might be smaller). `dustRelayFee` is set
to 3000 sat/kb, thus 110 * 3000 / 1000 = 330. As all time-sensitive
outputs are p2wsh, a value of 330 sat is the lower bound desired
to ensure good propagation of transactions. We give a bit margin to
our counterparty and pick up 660 satoshis as an accepted
`dust_limit_satoshis` upper bound.

As this reasoning is tricky and error-prone we hardcode it instead of
letting the user picking up a non-sense value.

Further, this lower bound of 330 sats is also hardcoded as another constant
(MIN_DUST_LIMIT_SATOSHIS) instead of being dynamically computed on
feerate (derive_holder_dust_limit_satoshis`). Reducing risks of
non-propagating transactions in casee of failing fee festimation.

fuzz/src/chanmon_consistency.rs

@@ -319,7 +319,6 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
 			let mut config = UserConfig::default();
 			config.channel_options.fee_proportional_millionths = 0;
 			config.channel_options.announced_channel = true;
-			config.peer_channel_config_limits.min_dust_limit_satoshis = 0;
 			let network = Network::Bitcoin;
 			let params = ChainParameters {
 				network,
@@ -339,7 +338,6 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
 			let mut config = UserConfig::default();
 			config.channel_options.fee_proportional_millionths = 0;
 			config.channel_options.announced_channel = true;
-			config.peer_channel_config_limits.min_dust_limit_satoshis = 0;
 
 			let mut monitors = HashMap::new();
 			let mut old_monitors = $old_monitors.latest_monitors.lock().unwrap();