Support corpus pruning with different sanitizers

[Dor1s]

We currently require ASan for corpus pruning. It is possible that we'll have projects without ASan jobs.

Example: google/oss-fuzz#2188 (comment) almost got landed with UBSan only. This one case might be fine, but if we start fuzzing other programming languages or even accommodate more Golang projects, it might be an issue.

The changes that would be necessary:

1. https://github.com/google/clusterfuzz/blob/master/src/appengine/handlers/cron/project_setup.py should add prune job template to at least one of the job being created, probably prioritizing ASan over others. Interesting question here, if UBSan is generally faster, should we prune with it instead?

2. process_sanitizer_options in https://github.com/google/clusterfuzz/blob/master/src/python/bot/tasks/corpus_pruning_task.py has to be more flexible and work not only with ASan