les: historical data garbage collection (#19570)

This change introduces garbage collection for the light client. Historical
chain data is deleted periodically. If you want to disable the GC, use
the --light.nopruning flag.

core/chain_indexer_test.go

@@ -236,3 +236,7 @@ func (b *testChainIndexBackend) Commit() error {
 	}
 	return nil
 }
+
+func (b *testChainIndexBackend) Prune(threshold uint64) error {
+	return nil
+}