Move fuzz tests into tests/fuzz (#22376)

This puts the fuzz tests in the same directory as other tests and eases
the integration in OSS-Fuzz

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

tools/fuzz_test.go → tests/fuzz/fuzz_test.go

@@ -1,7 +1,7 @@
 // Copyright 2023 The Gitea Authors. All rights reserved.
 // SPDX-License-Identifier: MIT
 
-package main
+package fuzz
 
 import (
 	"bytes"