Deduplicate digests from user configuration (#2522)

* deduplicate digests from user configuration

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* backout pointer reciever change on imageSource

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

---------

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

internal/file/normalize_hashes.go

@@ -0,0 +1,24 @@
+package file
+
+import (
+	"crypto"
+	"sort"
+
+	"github.com/scylladb/go-set/uset"
+)
+
+func NormalizeHashes(hashes []crypto.Hash) []crypto.Hash {
+	set := uset.New()
+	for _, h := range hashes {
+		set.Add(uint(h))
+	}
+	list := set.List()
+	sort.Slice(list, func(i, j int) bool {
+		return list[i] < list[j]
+	})
+	result := make([]crypto.Hash, len(list))
+	for i, v := range list {
+		result[i] = crypto.Hash(v)
+	}
+	return result
+}