cypress: Generate tests data once and get them through a task

Some cypress tests use input data generated before each test suite.

Some of these data are retrieved by sending HTTP requests to the
Software Heritage Web API, which can take some times, especially
when repeating that processing before each test suite.

So instead of sending those HTTP requests before each test suite,
prefer to do it once and put the test data in global cache. Those
data will then be set to test suite scope through the use of a
custom cypress task.