tlv+go.mod: generate inbound fee TLV type

Also add a temporariy replace to the tlv package which can be removed as
soon as the PR that includes this commit is merged and a new tag for the
tlv package has been created.

tlv/internal/gen/gen_tlv_types.go

@@ -22,6 +22,10 @@ const (
 	// second defined unsigned TLV range used in pure TLV messages.
 	pureTLVSecondUnsignedTypeRangeStart uint32 = 3000000000
 
+	// inboundFeeType defines the TLV type used within the channel_update
+	// message to indicate the inbound fee for a channel.
+	inboundFeeType = 55555
+
 	defaultOutputFile = "tlv_types_generated.go"
 )
 
@@ -29,6 +33,7 @@ const (
 var typeMarkers = map[uint32]struct{}{
 	pureTLVSecondSignedTypeRangeStart:   {},
 	pureTLVSecondUnsignedTypeRangeStart: {},
+	inboundFeeType:                      {},
 }
 
 const typeCodeTemplate = `// Code generated by tlv/internal/gen; DO NOT EDIT.