lnwire+feature: new zero-conf, scid-alias feature bit + chantypes

This defines the zero-conf feature bit, the scid-alias feature bit,
the zero-conf channel type, and the scid-alias channel type. It also
defines the dependency "tree" that exists for the feature bits.

The scid-alias feature bit signals that the node requires an alias
short channel id to be sent in funding_locked. The scid-alias channel
type requires that the channel is private, in addition to some other
forwarding-related privacy measures.

feature/manager.go

@@ -31,6 +31,15 @@ type Config struct {
 	// NoKeysend unsets any bits signaling support for accepting keysend
 	// payments.
 	NoKeysend bool
+
+	// NoOptionScidAlias unsets any bits signalling support for
+	// option_scid_alias. This also implicitly disables zero-conf channels.
+	NoOptionScidAlias bool
+
+	// NoZeroConf unsets any bits signalling support for zero-conf
+	// channels. This should be used instead of NoOptionScidAlias to still
+	// keep option-scid-alias support.
+	NoZeroConf bool
 }
 
 // Manager is responsible for generating feature vectors for different requested
@@ -125,6 +134,14 @@ func newManager(cfg Config, desc setDesc) (*Manager, error) {
 			raw.Unset(lnwire.KeysendOptional)
 			raw.Unset(lnwire.KeysendRequired)
 		}
+		if cfg.NoOptionScidAlias {
+			raw.Unset(lnwire.ScidAliasOptional)
+			raw.Unset(lnwire.ScidAliasRequired)
+		}
+		if cfg.NoZeroConf {
+			raw.Unset(lnwire.ZeroConfOptional)
+			raw.Unset(lnwire.ZeroConfRequired)
+		}
 
 		// Ensure that all of our feature sets properly set any
 		// dependent features.