tests/fuzzers: fuzzbuzz fuzzers for keystore, rlp, trie, whisper (#19910)

* fuzzers: fuzzers for keystore, rlp, trie, whisper (cred to @guidovranken)

* fuzzers: move fuzzers to testdata

* testdata/fuzzers: documentation

* testdata/fuzzers: corpus for rlp

* tests/fuzzers: fixup

tests/fuzzers/keystore/corpus/0176eaf52ed014ec5c91cf4afa070dd3fd469077-1

@@ -0,0 +1 @@
+ns<EFBFBD><EFBFBD>,<2C><>

tests/fuzzers/keystore/keystore-fuzzer.go

@@ -0,0 +1,37 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package keystore
+
+import (
+	"os"
+
+	"github.com/ethereum/go-ethereum/accounts/keystore"
+)
+
+func Fuzz(input []byte) int {
+	ks := keystore.NewKeyStore("/tmp/ks", keystore.LightScryptN, keystore.LightScryptP)
+
+	a, err := ks.NewAccount(string(input))
+	if err != nil {
+		panic(err)
+	}
+	if err := ks.Unlock(a, string(input)); err != nil {
+		panic(err)
+	}
+	os.Remove(a.URL.Path)
+	return 0
+}