Resolve "Integrate clusterfuzzlite/libfuzzer/oss-fuzz in the main core Kea repo"

Closes #3605 (closed).

• 4b5332fe Prepare existing code for fuzzing

  • Separate ENABLE_AFL into ENABLE_FUZZING and HAVE_AFL.
  • Add the --disable-unicode flag required in the oss-fuzz container.
  • Add checking of support for C++17.
  • Make Kea compile with afl++.
  • Rotate ports in getServerPort() functions under an env var.
  • Fix some destruction issues that would result in crashes when fuzzing.
  • Add some checks in the UnixControlClient that prevent some crashes when fuzzing.
  • Add isc::util::isSocket() function.
  • Change isc::util::file::Path to not append a trailing slash to allow chained calls of parentPath().
  • Add isc::util::file::TemporaryDirectory useful when fuzzing.

• fa39a1f4 Integrate a new fuzzing solution in Kea

  The solution is based on clusterfuzzlite, libfuzzer, and oss-fuzz technologies.

  • Add the .clusterfuzzlite directory.
  • Add the fuzz CI stage and fuzzing CI jobs.
  • Add the fuzzing targets in the fuzz directory.
  • Document fuzzing in doxygen.

Here's a todo list that I intended to turn into separate tickets after this MR gets merged, but if the reviewer insists, we could do them as part of this one as well.

1. Find a way to fetch results from fuzz-batch job and integrate them into the jenkins tests report. - We might need to wait until another crash happens, or intentionally cause a crash in order to have artifacts to work with.
2. Remove the requirement for input to be in hex format in packet-fuzzer.
3. See why fuzz-build job is not triggered.
4. Fix fuzz-coverage job. Needs clang++19.
5. Fix fuzz-prune job. Seems like external issue.
6. Create a simple way to replicate fuzzing errors locally, or document how to do it. - There is a run-locally.sh script, but it's improvised. The proper way to run locally according to oss-fuzz docs is to upload instructions on how to build Kea (see .clsuterfuzzlite) to the oss-fuzz repo, run their python script, which then downloads docker images that they build regularly (probably with updated seed corpus), and runs on those.