input: create new ScriptDesciptor interface

In this commit, we add a new interface, the `ScriptDesciptor` to
abstract over details of a given output script. The purpose of this
interface, and the taproot superset, is to be able to paper over the
differences of a p2wsh vs a p2tr output. With this new interface, we can
treat them as the same, but then use a type assertion to get at any
control block related methods if needed.

lnutils/memory.go

@@ -1,8 +1,21 @@
 package lnutils
 
-// PTr returns the pointer of the given value. This is useful in instances
+// Ptr returns the pointer of the given value. This is useful in instances
 // where a function returns the value, but a pointer is wanted. Without this,
 // then an intermediate variable is needed.
 func Ptr[T any](v T) *T {
 	return &v
 }
+
+// ByteArray is a type constraint for type that reduces down to a fixed sized
+// array.
+type ByteArray interface {
+	~[32]byte
+}
+
+// ByteSlice takes a byte array, and returns a slice. This is useful when a
+// function returns an array, but a slice is wanted. Without this, then an
+// intermediate variable is needed.
+func ByteSlice[T ByteArray](v T) []byte {
+	return v[:]
+}