[Fuzzing] Add fuzz testing

[0x34d]

using go-fuzz for fuzz testing of ldap

Error:

"PR / Go 1.16.x PR Validate . (Modules) (pull_request) Failing after 17s:"

vet: ./dn_test.go:294:29: F not declared by package testing
Error: Process completed with exit code 2.

Go-fuzz was introduce in Go 1.18.

[cpuschma]

Thank you for your PR. I've been keeping an eye on fuzzing for some time but didn't bring myself to do it yet 😄 I'm not very familar with Github Actions, cause this would break any checks for older Go versions.

If anyone can jump in and update the Github Actions to only run fuzzing on Go versions >1.18, I would very much appreciate that ❤️

[0x34d]

Review this hack.

[0x34d]

fuzz_test.go why a different file?

• It will prevent running tests on versions lower than go1.18 in this file.
• The filter_test.go file contains Benchmark tests, ClusterFuzz doesn't compile when Benchmark tests and Fuzzing tests are in the same file.