feat: Generate isr before begin block (cosmos#931)

Closes: cosmos#914

---------

Co-authored-by: Tomasz Zdybał <tomek@zdybal.lap.pl>

state/executor.go

@@ -322,8 +322,7 @@ func (e *BlockExecutor) execute(ctx context.Context, state types.State, block *t
 	currentIsrIndex := 0
 
 	if e.fraudProofsEnabled && currentIsrs != nil {
-		expectedLength := len(block.Data.Txs) + 2
-		// BeginBlock + DeliverTxs + EndBlock
+		expectedLength := len(block.Data.Txs) + 3 // before BeginBlock, after BeginBlock, after every Tx, after EndBlock
 		if len(currentIsrs) != expectedLength {
 			return nil, fmt.Errorf("invalid length of ISR list: %d, expected length: %d", len(currentIsrs), expectedLength)
 		}
@@ -345,6 +344,15 @@ func (e *BlockExecutor) execute(ctx context.Context, state types.State, block *t
 		}
 	})
 
+	if e.fraudProofsEnabled {
+		isr, err := e.getAppHash()
+		if err != nil {
+			return nil, err
+		}
+		ISRs = append(ISRs, isr)
+		currentIsrIndex++
+	}
+
 	genAndGossipFraudProofIfNeeded := func(beginBlockRequest *abci.RequestBeginBlock, deliverTxRequests []*abci.RequestDeliverTx, endBlockRequest *abci.RequestEndBlock) (err error) {
 		if !e.fraudProofsEnabled {
 			return nil