swap format readseekers for readers (#2515)

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

syft/format/internal/stream/seekable_reader.go

@@ -0,0 +1,24 @@
+package stream
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+)
+
+func SeekableReader(reader io.Reader) (io.ReadSeeker, error) {
+	if reader == nil {
+		return nil, fmt.Errorf("no bytes provided")
+	}
+
+	if r, ok := reader.(io.ReadSeeker); ok {
+		return r, nil
+	}
+
+	content, err := io.ReadAll(reader)
+	if err != nil {
+		return nil, err
+	}
+
+	return bytes.NewReader(content), nil
+}