test/fuzz: move fuzz tests into this repo (#5918)

Co-authored-by: Emmanuel T Odeke <emmanuel@orijtech.com>

Closes #5907

- add init-corpus to blockchain reactor
- remove validator-set FromBytes test
now that we have proto, we don't need to test it! bye amino
- simplify mempool test
do we want to test remote ABCI app?
- do not recreate mux on every crash in jsonrpc test
- update p2p pex reactor test
- remove p2p/listener test
the API has changed + I did not understand what it's tested anyway
- update secretconnection test
- add readme and makefile
- list inputs in readme
- add nightly workflow
- remove blockchain fuzz test
EncodeMsg / DecodeMsg no longer exist

test/fuzz/mempool/checktx.go

@@ -0,0 +1,34 @@
+package checktx
+
+import (
+	"github.com/tendermint/tendermint/abci/example/kvstore"
+	"github.com/tendermint/tendermint/config"
+	mempl "github.com/tendermint/tendermint/mempool"
+	"github.com/tendermint/tendermint/proxy"
+)
+
+var mempool mempl.Mempool
+
+func init() {
+	app := kvstore.NewApplication()
+	cc := proxy.NewLocalClientCreator(app)
+	appConnMem, _ := cc.NewABCIClient()
+	err := appConnMem.Start()
+	if err != nil {
+		panic(err)
+	}
+
+	cfg := config.DefaultMempoolConfig()
+	cfg.Broadcast = false
+
+	mempool = mempl.NewCListMempool(cfg, appConnMem, 0)
+}
+
+func Fuzz(data []byte) int {
+	err := mempool.CheckTx(data, nil, mempl.TxInfo{})
+	if err != nil {
+		return 0
+	}
+
+	return 1
+}