Support custom forks in test suites jobs

Support custom forks in test jobs (MTT, kiali-int, kiali-cypress)

When I did some changes or fixes in MTT, kiali-int, kiali-cypress test suites, I would like to check if all test suites are working with my changes. Right now, there is no way to run a test job with a custom GitHub fork. The only way is to run the whole test suite locally or in local Jenkins (with pipeline code changes).