mempool: length prefix txs when getting them from mempool (#5483)

## Description

In protobuf `[]byte` is varint encoded. When adding txs to the block we were not taking this into account. 


Closes: #XXX

state/execution.go

@@ -104,6 +104,7 @@ func (blockExec *BlockExecutor) CreateProposalBlock(
 
 	// Fetch a limited amount of valid txs
 	maxDataBytes := types.MaxDataBytes(maxBytes, evSize, state.Validators.Size())
+
 	txs := blockExec.mempool.ReapMaxBytesMaxGas(maxDataBytes, maxGas)
 
 	return state.MakeBlock(height, txs, commit, evidence, proposerAddr)

state/tx_filter_test.go

@@ -25,8 +25,8 @@ func TestTxFilter(t *testing.T) {
 		tx    types.Tx
 		isErr bool
 	}{
-		{types.Tx(tmrand.Bytes(2154)), false},
-		{types.Tx(tmrand.Bytes(2155)), true},
+		{types.Tx(tmrand.Bytes(2151)), false},
+		{types.Tx(tmrand.Bytes(2152)), true},
 		{types.Tx(tmrand.Bytes(3000)), true},
 	}
 
@@ -37,7 +37,7 @@ func TestTxFilter(t *testing.T) {
 		state, err := stateStore.LoadFromDBOrGenesisDoc(genDoc)
 		require.NoError(t, err)
 
-		f := sm.TxPreCheck(state) // current max size of a tx 1850
+		f := sm.TxPreCheck(state)
 		if tc.isErr {
 			assert.NotNil(t, f(tc.tx), "#%v", i)
 		} else {