Backfill Blobs (#13595)

* retrieve and save blobs during backfill

* Update beacon-chain/sync/backfill/batch.go

Co-authored-by: Preston Van Loon <pvanloon@offchainlabs.com>

* Update beacon-chain/sync/backfill/blobs.go

Co-authored-by: Preston Van Loon <pvanloon@offchainlabs.com>

* Update beacon-chain/sync/backfill/metrics.go

Co-authored-by: Preston Van Loon <pvanloon@offchainlabs.com>

* make blobSync initialization path a little safer

* use bytes.Equal to avoid extra allocation

* stop using log.Fatal and other little cleanups

* wrap up post blob sync actions in batch mutator

* unit test coverage on verifier

---------

Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>
Co-authored-by: Preston Van Loon <pvanloon@offchainlabs.com>

beacon-chain/sync/backfill/batch_test.go

@@ -0,0 +1,21 @@
+package backfill
+
+import (
+	"testing"
+
+	"github.com/prysmaticlabs/prysm/v4/consensus-types/primitives"
+	"github.com/prysmaticlabs/prysm/v4/testing/require"
+)
+
+func TestSortBatchDesc(t *testing.T) {
+	orderIn := []primitives.Slot{100, 10000, 1}
+	orderOut := []primitives.Slot{10000, 100, 1}
+	batches := make([]batch, len(orderIn))
+	for i := range orderIn {
+		batches[i] = batch{end: orderIn[i]}
+	}
+	sortBatchDesc(batches)
+	for i := range orderOut {
+		require.Equal(t, orderOut[i], batches[i].end)
+	}
+}