[11.x] Name of job set by displayName() must be honoured by Schedule

[SCIF]

Queue jobs could have displayName() method providing a better naming than just a plain classname. This name is currently honoured by a queue worker but a queue scheduler. This PR fixes this inconsistency

[SCIF]

This is the version of #50961 without BC brake.

[SanderMuller]

@SCIF you could update the code to only use the displayName() method when the job() method already receives an instance. This prevents creating an instance for calls that explicitly pass the class string (potentially doing this avoid creating an instance)

$name = !is_string($job) && method_exists($job, 'displayName')
    ? $job->displayName()
    : get_class($job);

[SCIF]

@SanderMuller , thank for spotting this! I took the creation of the object out of the callback which is a bad idea. Will prepare a fix soon, including tests changed.