Move scripts used in CI to the new location (#5198)

* Move CI scripts and update references

* Update paths in .gitlab-ci.yml

* Removed outdated entries from CODEOWNERS

polkadot/scripts/ci/github/run_fuzzer.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+timeout --signal INT 5h cargo hfuzz run $1
+status=$?
+
+if [ $status -ne 124 ]; then
+  echo "Found a panic!"
+  # TODO: provide Minimal Reproducible Input
+  # TODO: message on Matrix
+  exit 1
+else
+  echo "Didn't find any problem in 5 hours of fuzzing"
+fi