Fix custom tokenizers test
# What does this PR do?

The custom tokenizers tests were never run because the test fetcher was not run before we look at its output to decide whether or not to run the tests. This PR fixes that and also adds missing tests to the nightly suite.
_The documentation is not available anymore as the PR was closed or merged._<|||||>@ydshieh Those three files contain tests that require some specific dependencies to be installed (ftfy for openai and clip). So in the other test jobs, those tests are never run.