Auth: Make `ilSessionTest` work

[mjansenDatabay]

The tests in ilSessionTest are always ignored and reported as "skipped" when executing our PHPUnit test suite.

• With this PR I mocked the database by delegating calls to the ilDBInterface to an "in memory" database (PDO sqlite).
• Furthermore I removed a method which was/is not a test method at all: tstBasicSessionBehaviour

There is an alternative to this PR: Completely delete the test file. Since the code unter test only contains wrapped database calls, it is IMO only possible to test the database calls.

[pascalseeland]

The main reason why I did skip the old ilSession test was because it was flappy. The issue occured because of https://github.com/ILIAS-eLearning/ILIAS/blob/30e89b3bb44ea6bf4031d3d3563147fc5089ab2e/components/ILIAS/Authentication/classes/class.ilSession.php#L194C1-L199C1, which did run on arbitrary times. With the cron check around it, I would propose the following:

• [x] Keep the old test with methode renamed back to testBasicSessionBehaviour
• [x] Add a mock to that test that will return true when querying of the job auth_destroy_expired_sessions is active
• [x] Add the current test as a second test

[mjansenDatabay]

@pascalseeland Done

[mjansenDatabay]

@pascalseeland This is ready to merge. I you don't have any objections, go go go!

[mjansenDatabay]

Merged, with all checklist items completed!