[5.5] add allOnQueue and allOnConnection for job chaining

[themsaid]

Having:

JobA::withChain([
    (new JobB())->onQueue('second')->onConnection('connection2'),
    (new JobC()),
])->dispatch()
   ->allOnQueue('first')
   ->allOnConnection('connection1');

• JobA will run on first queue and on connection1.
• JobB on second queue and on connection2.
• JobC on first queue and on connection1.

The new allOnQueue and allOnConnection methods will instruct the dispatcher to use the given queue/connection if no queue/connection was set explicitly on each job.

The old behaviour remains the same thus this PR is not a breaking change.

[Artistan]

This does not support having the chain connection change with the next job having the queue/connection already set...

$next->chainConnection = $next->chainConnection??$this->chainConnection;

[themsaid]

Yeah we don't want to do that, the chain connection is declared once and used as a default connection for when no connection is specified.

[Artistan]

Interesting. I am not sure why that was not communicated on my pull request. Keeps it simpler, Thanks.

[Artistan]

#21568 (comment)
FYI, I was told this would need to be a 5.6 feature...

[themsaid]

@Artistan because in your PR you've changed the method signature.

[taylorotwell]

So you call these methods after dispatch?

[themsaid]

@taylorotwell yes, the methods exist in PendingDispatch

[taylorotwell]

Ah OK I see.