[8.x] Set chain queue and connection only when explicitly configured

[themsaid]

This PR fixes #35041

It sets the chain queue and connection only when specified. Otherwise the dispatcher will push each job in the chain to the queue/connection assigned to it.

[hivokas]

Should we also do the same with delay and maybe other properties?

[themsaid]

@hivokas did it for delay as well.

[taylorotwell]

Is this the behavior we want? For example, if I do:

Bus::chain([
    (new Job1)->onQueue('foo'),
    new Job2,
])->onQueue('bar');

Don't I want Job1 to still run on the foo queue since I explicitly specified it? While Job2 would run on the bar queue since it had no explicit queue specification?

[hivokas]

@taylorotwell @themsaid thanks guys!