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.

eth/bloombits.go

@@ -136,3 +136,8 @@ func (b *BloomIndexer) Commit() error {
 	}
 	return batch.Write()
 }
+
+// PruneSections returns an empty error since we don't support pruning here.
+func (b *BloomIndexer) Prune(threshold uint64) error {
+	return nil
+}