ethdb/pebble: fsync for batch writes (ethereum#27522)

This is likely the culprit behind several data corruption issues, e.g. where data has been
written to the freezer, but the deletion from pebble does not go through due to process
crash.

ethdb/pebble/pebble.go

@@ -535,7 +535,7 @@ func (b *batch) Write() error {
 	if b.db.closed {
 		return pebble.ErrClosed
 	}
-	return b.b.Commit(pebble.NoSync)
+	return b.b.Commit(pebble.Sync)
 }
 
 // Reset resets the batch for reuse.