negentropy: refactor for allowing different types of storage.

nip77/negentropy/storage.go

@@ -0,0 +1,13 @@
+package negentropy
+
+import (
+	"iter"
+)
+
+type Storage interface {
+	Size() int
+	Range(begin, end int) iter.Seq2[int, Item]
+	FindLowerBound(begin, end int, value Bound) int
+	GetBound(idx int) Bound
+	Fingerprint(begin, end int) [FingerprintSize]byte
+}