core, eth/downloader: handle spurious junk bodies from racey rollbacks (#25578)

* eth/downloader: handle junkbodies/receipts in the beacon sync

* core: check for header presence when checking for blocks

core/blockchain_reader.go

@@ -137,6 +137,9 @@ func (bc *BlockChain) HasBlock(hash common.Hash, number uint64) bool {
 	if bc.blockCache.Contains(hash) {
 		return true
 	}
+	if !bc.HasHeader(hash, number) {
+		return false
+	}
 	return rawdb.HasBody(bc.db, hash, number)
 }